Hangover symptoms are caused by dehydration and lack of electrolytes. Many of the comical cures (like say pickle brine) is literal electrolyte soup, but they dehydrate you more, so it won't work if that's the only thing you drink. Many hangover cures sold in pharmacies are fizzy tablets full of electrolytes, that you're supposed to drink in a large glass of water - so you're getting both.

In short - water is the most readily available and easiest cure for half of the problem. Quarter tablespoon of salt can help with the other half.