I find Gatorade quite useful. It's got some simple carbs and some electrolytes, and as I'm a big guy who lives in a hot climate and sweats like a pig, I feel quite a bit better during and after rides when I drink it as compared to plain water. Machka is certainly right in that there are better drinks, but Gatorade does the job for me at a very low price and with easy availability.

None of which, of course, means that it's necessarily right for anyone else. I do know several people who have to cut in half with water in order to avoid bloating and stomach cramps.