What were you drinkin'? Bucketloads of Mountain Dew?
I can only have the caffiene-free stuff. Root beer's my favorite. Followed by caffiene-free Pepsi. I can sometimes handle a little bit of regular Pepsi, but any more caffiene than that and the headaches start. Fairly recently, I was at an Xbox LAN party, and they were handing out Mountain Dews, but I wasn't watching so I just popped the tab and started drinking. On the way home(strangely enough, these caffiene aftereffects only seem to hit me AFTER I'm done playing video games), the headaches got so bad that I got carsick. That night sucked so bad.....
(On the other hand, I did whomp everyone really bad at Halo 2 that night. So they set my handicap up to Mild, then Moderate, and when I was still crackin' heads on Severe, they knew I was on something! Makes me wonder if the side effects are really worth it...)