My brothers best friend (my friend too) went on a two year speed binge and he says is if you drink a six pack of red bull in a 10 minute period you will destroy your heart and get a rush very similar to speed. So drink in moderation. I don't really trust a lot of things he says, he is isn't the smartest person in the world, but hey its possible.
This is real life, just to answer your question. Go take a nap and have fun with that headache when you wake up. (at least i get headaches from too much guranna (SP?))