energy drink
Drinks you can usually buy easily that cause you to become very concentrated mentally and hyper. As was said before, Boo Koo is a great example of this. I haven't tried Monster Assault yet, though. From personal experience(though things may be different from individual to individual), chugging brings best results.
Boo Koo, Monster Assault, Sobe Adrenaline Rush, Red Bull, etc.