I cured hangovers by not drinking till I was retarded.
I'm shocked that nobody has said McDonalds. I thought this was widely known to everyone as the hangover cure for the ages.
If it is the breakfast menu get one or two of the biscuits sandwiches, hash brown, and a large coke (I know a coke is weird with breakfast - trust me on this one guys).
If it is lunch menu go with a quarter pounder or a double QP (if you can handle it), large fries, large coke (the coke is key for settling your stomach). Within 5 minutes of finishing you will be a new man.
Last hangover I had was when my sister got married. My dad who never drinks was kicking them back like a pro - so I felt the need to at least keep up with him. Needless to say I was in a bad place the next day till I hit up the golden arches. Worked like a charm.