Being a veteran in the hangover department I can tell you without a shadow of a doubt that coconut water is the one and only cure for a hangover.

It has more electrolytes than Gatorade and rehydrates you with the perfect balance of minerals, sugars and salts to take your body out of 'hangover' state.  This means you'll be able to eat, preferably something healthy that can absorb the alcohol (grease will kill you).

Happy drinking!