It sounded like you were referring to Energy drinks (the other people replying to the post seemed to draw the same conclusions). My point was, if you need a stimulant stronger than a cup of coffee (35 mg of caffeine) then you probably needed more sleep/rest the night before.
That being said... for supplements in general. I do like Sportslegs
(helps with lactic acid burn) and Recovery-ease
(lessens muscle soreness after workout). Neither of those are stimulants and neither will actually help you ride... they just let you ride longer and not feel so beat up the next day.