When one has drunk too much caffeine the previous day, It resulted in a hangover the next, Also Know as CH!
Examples of a caffine hangover include:
Being Ratty with everyone and everything
"Woah, Whats up With Jenny?"
When you've drunk so much caffeine that you become mildly to moderately dehydrated, resulting in a sensation similar to a hangover.
Caffeine, like alcohol, is a diuretic (a substance that makes you pee a lot), and much of the "hangover" symptoms -- nausea, vomiting, headache, dizziness, etc. -- are a result of being dehydrated.
The best way to avoid getting a caffeine (or alcohol) hangover is to not only limit your intake of caffeine or alcohol, but to also drink plenty of water, or better yet sports drinks like Powerade or Propel, to keep yourself hydrated while you party. You may look like a dork doing it, but you'll fare a lot better than your friends will in the morning.
Sports drinks are also the best and quickest hangover cure because they not only hydrate you, but replenish your electrolyte balance as well.
Jim had to stay up late last night for the Halo tournament, so he drank nothing but Full Throttle. I drank just as many cans, but I also drank a bottle of lemon Propel in between. He got the caffeine hangover, but I feel ready for another round.