Ephedrine ;)... oh wait... you can prolly take a lot of different things and get energy i.e. caffeine, Dimeth, ephedrine, speed, cocain... (jk bout speed and cocain)
even though they say males peak at 18 and by 21 there bodys are done growing. It is not always the case and some people could still be developing till 22 or past... depends on the person.