Hangover symptoms are from dehydration. Drink water.
Some is from methanol poisoning from wines and cheap liquor.
In a hangover, you are dehydrated, and your sugar has tanked as has your supply of B vitamins. So anything wet could help, a LITTLE something sweet, and a multi-B pill should help. None of which are sourced by anyone who can afford and is financially motivated to shell out the many millions it costs to get the approved studies. Also bitters are amazing as a preventive. Then if you really mess up, coffee enemas.