I'll add my vote for Electro-Mix/-Lite/Whatever it's called. Small packets, easy and light to carry, not much taste, can be mixed with every liquid I've tried it with so far. Pretty close to perfect. So far the best combo is one packet in a really big glass of iced tea and, um, an amount of dumb old table sugar.

One recovery beverage that hasn't been mentioned here that I really like is a smallish glass of diluted orange juice mixed with a heaping teaspoon of brewer's yeast. (OK, I'm just an old hippy. It's cool.) I've use that for years to put some bounce back in my step. It's kind of a mess, though, so I just drink it at home.