Mostly I like plain water. If (really big if) I remember, I stick a half-full bottle of water in the freezer at night, and top it off when I go out. The water stays cold for whole minutes!

I've also been known to carry a bottle of plain iced tea.

Once in a very great while a can of Red Bull well diluted with ice is along on my rides, but I can do without, generally.

I'm not a Gatoraid drinker.