while Rockstar contains 160 mg, albeit in a larger 17-ounce can. But what energy drink has the absolute most caffeine? Well, for a while, it was something called Redline Xtreme, but that's since ...

and Rockstar Xdurance. Each of these packs a 300-milligram caffeine wallop per can. To put that in perspective, Red Bull, which is the best-selling energy drink in the U.S., contains a ...