At uni i did basically 3 exams without sleep. Not my choosing, i just couldn't sleep the night before each exam. Probably due to a bit of stress/nervousness and information running in and out my brain.
I didnt get out of bed and run around or anything, i just lay there trying to sleep. 2 of the exams were at 9am so they werent to bad. Even though you havent got sleep you have been resting so it wasnt that bad. At 7:30 i drove to down to the local 24 and got a coke and a couple of milo energy bars, then at 8:30 went down and got a red bull and that technique had me fine for the exam.
The last exam when i couldnt get any sleep was an exam that was in the afternoon starting at 2 o'clock. Just lay there again trying to sleep and come 9:30 am i still havent slept at all bar about 30-40 minutes. So got out of bed and just did normal stuff, ate a lot of high energy food which woke me up and i was fine for the exam and completely anhilated it. I showed no mercy towards it.
The key was though that i had studied hard for all the exams so i knew the content and not having any sleep isnt going to change the fact that you know the content required. When people say the sleep is the most important thing before an exam, tell tehm to get stuffed, the most important thing is you know the work.