I haven't tried any of them. If I need caffeine, I turn to soda or a cup of tea, I don't need a super-charged hit of energy drink. After 5 years of university I saw too kids cracked-out on the stuff to ever want to try it. I'm sure they drank way too many of them for their own good, and it wasn't like a single can of Red Bull did them in, but watching kids twitch, rave, fidget and babble incoherently sort of turned me off on the whole craze.