Red Bull is my favourite, even though there is  so many health concerns.  You aren't suppose to drink more than 2 a day, the caffine and taurine increases your heart rate.  And in Canada it's ilegal to mix it with alcohol because it increase your heart rate even more, and just gets you wired.
I was doing a 24 hours race biking, and I was captain, and needed to stay up all night. I had 6 Red Bull's with in 3 hour range, two of them were with vodka. I was wired like a microwave, plus teh coffee I drank.