One time I actually swallowed two tablespoons of instant coffee because I needed to wake up desperately, and didn't have much time before I had to leave. I followed it up with a Diet Coke or two to wash the taste out. I guess that wasn't technically an energy drink, but it had a similar effect. I was able to see a weird vertical line scanning across a CRT monitor I had at the time that I normally couldn't see. What was that?