Caffiene doesn't do it for me anymore, so I've been experimenting with energy drinks. They seem to work better, but generally taste awful (Red Bull is the prime offender).
Taurine was originally extracted from bull's balls and hence when you drink a RedBull, you are giving a bull a ... lets say, doing a bull a favor :-)
(Taurine is not extracted from bull semen nowadays, of course ( probably coz this is not scalable :-p ) and it is claimed that the whole Tauine-Bull thing is a myth... but myths are fun to propagate)
If you're willing to branch out into other stimulants, I'd strongly recommend Kratom, feel free to ask if you have any questions.