I'm with Masa on this one. There's nothing so awesome as a glass of water. The best part is that it's free. I take my Nalgene full of water with me wherever I go.

In terms of not so healthy, I really love Dr. Pepper. And for a while I was addicted to Vanilla Coke. It was weird. The first time I drank it I hated it, and then after a while, I really loved it, and then after using it as my beverage of choice to keep me awake while writing all-night lab reports (cause I don't really like coffee or tea), I can't say that I like it as much anymore.

As for alchohol, I'm fairly partial to peach schnapps and Sprite, as well as rum and coke. I usually have beer though.