quick answer,.... anything you dont mind tasting twice,.... ice cream? that your sure you can throw up easily without chunks!
longer answer,... anything that sounds good,... comfort foods,... each person is SOO very different for this,.. there is no magic bullet.
the serious drinker will give you the old "hair of the dog" schpiel,... but unless your a serious drunk i wouldnt advise it,... and if your a serious drunk you dont need hangover advice, ha!
take tylonol and potasium as soon as you can hold things down on your stomache. the worst WORST cause of the hangover is A) the effects of the alchohol on the brain,... B) the dehydration caused by the alchohol in your system. the tylonol will help your battered brain and the potasium will replenish your body of all you donated to the pubs plumbing the night before.
you need clear fluids and comfort foods that will sit well on your stomache,.... you'll learn what works for you,..... or you'll learn to drink iced tea.