Just stumbled upon a nice little movie about the different drinks that are known/unknown in Germany vs. the USA:
As you see, we Germans really like our mixed drinks. Here's a bit more information on those drinks, as the movie shows the how and the what, but doesn't mention the why:
This is a mix of beer and sweet plain soda. As far as I know the original lemonade used (Chabeso) was a little more diverse than Sprite, with fruity and lactoserum aftertaste, but commonly you just get beer mixed with Sprite. It's essentially thinned, sweeter beer, and a good choice of drink when you're not planning to get drunk. The "girls' drink" comment really only applies because of that. If you're one of the people who see beer as an alcohol-drinking competition, don't order Radler, but otherwise it is just fine.
Some breweries sell Radler as a pre-mixed drink, but I usually mix it myself, as do most good restaurants, and the BiergÃ¤rten which are so common all over Germany.
There are many kinds of Schorle, i.e. mixes of fruit juices with sparkling water. The advantage of Apfelschorle is that it is isotonic, i.e. it is "thicker than water, but thinner than juice", and thus ideal for being absorbed by your body. You could say it's a natural sports drink. You can get Apfelschorle in pretty much every restaurant or cafe in Germany, and many places also offer various other sorts of Schorles. The second-most-common is probably the one with orange juice (O-Saft-Schorle or Orangensaftschorle).
At least Apfelschorle can be purchased as a pre-mixed drink, but pretty much all of these I've tried so far are much thinner than the typical real Apfelschorle, and are artificially sweetened. The Coca-Cola-equivalent is a lemonade called "Lift" that you can get at Kiosks and Vending machines pretty much everywhere. Again, IMO it's not as good as hand-mixed Apfelschorle, and tastes a lot stickier and more artificial.
In some areas of Germany, you can also order Weinschorle, i.e. Wine mixed with sparkling water. French people tend to react a bit disturbed when they hear about this.
Spezi is a mix of Fanta Orange (the yellow-ish kind that you get in Germany, not the reddish kind in the movie) or any other kind of Orange soda ("Orangenlimonade") with Cola. "Spezi" is a brand name licensed to a group of breweries and thus understood in pretty much all of Germany, in other places you may find it under the generic name "Cola Mix" or the brand names "Mezzo Mix" or "Schwipp Schwapp". This one is fine if you buy it pre-mixed. It gives your Cola a nice, natural, orange-ey taste, not unlike squeezing lemon into it.
In general, beer mixes apart from Radler aren't that well-regarded in Germany. There has been a push in recent years by some beer manufacturers to establish some of their pre-mixed beers as trendy youth drinks, which seem to be making some inroads, but they're not readily available in restaurants yet.
In the state of Baden-Württemberg, Bananenweizen (banana juice mixed with wheat beer, "Bannanen-Weizen") is readily available, but both in Bavaria and Hessia I got looked at oddly for ordering one. They generally don't have it on the menu, and in Hessia I was given banana juice and Weizenbier separately with the understanding that I "would perform this crime" myself. Like Radler, these mixes lower the alcohol content, sweeten the drink a bit, and in the case of banana juice also help bridge the gap to the next meal a bit better.
Of course, there are some mixes created from necessity, where youths will mix their own Cola-Bier (aka Krefelder, Mazout and many other names) to sneak beer into events disguised as harmless coke and the likes. Note that the terms "Diesel" and "Moorwasser" are understood differently depending on what area you are in. In most places they refer to a Cola-bier, but in some areas are understood to be Spezi instead.
And a few bonus drinks:
This is a typically Swiss drink that tastes somewhere between Apfelschorle and wine (though it is a sweet, completely nonalcoholic lemonade). Many Germans find it really odd, but it is very common in its homeland, and you can get it everywhere there. What's special about this drink is that it contains "lactoserum", which is a milk extract (that tastes nothing like milk) that leaves an interesting aftertaste. Aforementioned Chabeso contains the same substance.
Rivella comes in 4 flavors, indicated by the color of the label: the original is "Rivella Red", of which there is a low-calorie, sugar-free variant "Rivella Blue". "Rivella Green" is made the same way, but is actually based on green tea extracts, and "Rivella Yellow" is made from soy milk instead of cow's milk.
It's fairly uncommon in Germany, but can be obtained in the specialty food sections of bigger shopping centres like Galeria Kaufhof or Karstadt, and they're becoming more common in supermarkets.
This is a typically Austrian drink, a herbal lemonade. It looks suspiciously like Rivella, but tastes noticeably different. Sweet, and as you expect, it tastes not unlike herbal tea, but as a lemonade. Almdudler is a bit easier to find in Germany, and in Bavaria in particular, but you may have to go into the specialty food section in some shops.
Legend has it that Fanta was created by Coca Cola dependencies in Germany during the war, when the ingredients for Coke became unavailable, out of whatever they had left. The word "Fanta" in Germany, although a brand name, is pretty much synonymous with any kind of orange soda ("Orangenlimonade"), so if you order one, don't be surprised to get the other. Sometimes you even get "Orangina" instead (which is an orange soda containing pulp), but usually they warn you in that case. You can get some other flavors of Fanta in Germany these days, but usually they're explicitly mentioned on the menu in restaurants if they have them.
If you order a lemonade in Germany, it is generally understood that you are requesting a sweet lemon soda, not real sugared lemon juice like you can get it in the USA. You may even get Sprite (which is strictly spoken a sweet soda or sweetened mineral water and doesn't contain lemon). Sometimes this is also referred to using the generic term "Süßer Sprudel".
If you are looking for real lemonade, you'll usually find it under the moniker "home-made" ("hausgemachte Limonade"), if they have it at all. But again, be careful, it's not unusual to find home-made "Ginger-lemonade" or "Elderberry-lemonade", which does not necessarily contain lemon. The German word for lemon is "Zitrone", so we re-defined that word to mean something else.
It is hard to get root beer in Germany. For a while Subway's used to offer root beer, but apparently that didn't sell enough, because more and more stores have stopped carrying it. You may get it in the specialty food sections of supermarkets if you're lucky, or in Asia specialty stores (the kind that carry stuff like Horlix, Marmite, etc.). The closest I've seen that, while rare, seems to be more and more readily available is Dr. Pepper. But that's not really root beer.
For the Germans among you: Root beer is a brown lemonade that tastes sort of like liquid bubble gum.
I've found exactly one store that carried Cream Soda. It was a supermarket that carried a bunch of foreign products in one aisle, including Root Beer, Dr. Pepper, Marmite, etc., only in cans, and not often. It's pretty much impossible to find.
For the Germans among you: Think of Cream Soda as a soda not unlike root beer with the taste of the "Werther's Original" candies.
Usually Germans just order "Cola", and you may get any brand, be it Coke, Pepsi, Afri Cola or a generic brand. You can get Light (i.e. low-calorie or "diet") colas at any restaurant as well, but sometimes they're a different brand than the full-calorie version. If you have a preference, you can usually ask and the waiter will tell you. Coke is definitely the most common brand, and sometimes if you order a "Coca Cola" the waiter will warn you if they carry Pepsi only.
Afri Cola is a German brand with higher caffeine content. It is considered somewhat of a distinguished taste to buy that in favor of Coke or Pepsi, and far less commonly available. However, they have a comparatively big mind share due to their being "local" and a run of very artistic TV ads from time to time
Do not expect restaurants to carry both Pepsi and Coke. It happens, but in general, restaurants are owned by a brewery and only rented out to the people making the food, and first and foremost carry that brewery's drinks, and don't carry the competition.
These days there is a legally mandated deposit on bottles and cans in Germany. There are a few exemptions (for milk, juice, schnapps and cider, I think), but you will want to return your bottles and cans to the store. Imported beverages are subject to this as well, so if you manage to find Root beer, don't take off the stickers with the bar code and recycling logo.
Any other ideas about German/US drinks, differences and pitfalls? Let me know in the comments.