When I have to stay up, I go with these. I really dig the Rojo Tea (red one) and the Lemonade/Iced Tea (yellow). Non carbonated, as I hate the carbonated energy drinks. Pretty much tastes like a sugary tea. And wow do they work. 6ish hours I'm good for per.
Rockstar has a non carbonated type, but they taste of chemicals too much.
Random babble from my sleep deprived brain.