There was a six month period back in college where I grabbed a Red Bull every morning on my way out the door. Somehow I had convinced myself that this was the right direction to take since I hated the taste of coffee. Then there was this super charged drink sold at Duane Reade that I used to purchase on really long days in the office. It made me incredibly jittery, and in my mind kept me going. 
Those drinks that supposedly gave me a mental edge are now outselling iced tea and sports drinks. However, research shows that all those ingredients included in them, aside from caffeine, have little, if any benefit at all. Despite what the energy drink makers WANT you to think, it is all about the caffeine--you simply feel it quicker because you can chug it down faster or its concentrated.
I know my gel that has caffeine in it makes my legs feel looser and it certainly comes in handy during those long runs. I couldn't imagine taking down a 5-Hour Energy before a 20 mile run though.
This NYT article breaks down the history of energy drinks and some of the ingredients in them. It is a real interesting read.
I don't know what stopped me from drinking those energy drinks. Maybe I just realized I liked tea more and there was less sugar.
Have you ever bowed to the powers of energy drinks?