title_body: Which beverages are least likely to give one a hangover? What induces hangover on a drink-to-drink basis?
upvoted_answer: Two things have to be considered:
  
  
  The first, as Lying Dog said, is impurities. In fact, if they give taste, they also give you hangover
  The second, much more important is the fact that alcohol is diuretic. Once drunk, the alcohol is converted into several substances (in several steps) by your liver. The problem is once the last substances cannot be converted into anything useful, it will be ejected from your body. How ? By urinating. But urinating requires water. The problem is that if you do not drink water as much as needed, your body will take it from where it can, including from your brain. Now think about a sponge left without water inside and you'll have a good idea of what your brain looks like after a night, inducing hangover the next morning.
  
  
  To answer your question, yes, Vodka is the most efficient alcohol to avoid hangover. But you can also avoid it by drink enough water while drinking alcohol (typically, if I'm at a party where I drink a lot of alcohol, I drink a pint of water after 2 or 3 beers)