Bananas,as many as you can eat. Plenty of fluid too (non-alcoholic obviously). It is the dehydration that causes hangovers,you need to replace the fluid you have lost as well as the minerals. Bananas contain potassium which is what you would be given in hospital if you had alcohol poisoning.
If you wake up and feel bad, try to sleep an extra hour or so. Then have bacon and eggs. Small glass of fresh orange juice. Then water for the rest of the day.
Drinking different types of alcohol is bad.Try and stick to one type of drink.