Yes definitely water...plus vitamin C and Vitamin B tablets you will wake up like its a normal day. The problem is most of the time I get in so late I just hit the bed and forget all about the possible hangover the next day..
Interestingly as a result I just bought "Chaser" last weekend after a hangover and tried it out on Saturday night (its tablets that are taken while you drink)..I guess it worked fine but I kind of took it easy that night so it is hard to tell..The vitamins and water are certainly more economical..Chaser was 6.99 for 10 tablets and you can take anywhere from 4-6 per night!!
'Chaser' is a brand name for RU-21. It works if you take one with every drink. As for the cost, just think of it as an extra $.70/drink. That's not too outrageous.