Emergence-C (I like the Joint Health formula)
Crystal Light Hydration (often combined with Emergence-C)
Zip Fizz (special treat, way too much packaging!)
Muscle Milk (sometimes with Emergence-C)
I never was a big fan of special drinks, always preferring plain water, but when you have to drink so much all the time, I found that flavored drinks helped keep my hydrated. It's much easier to gulp down a liter of water all at once if it's tasty.