water?!?!?!, drinking water when you wake up with a hangover is the absolute worst thing you could ever possibly do, it will totally bring back the effects 10 times fold and most likely even make you puke. It will increase your headache by 5000%. I think anyone who says to drink water after a hangover, never had a hangover ever
You can drink water while drinking and before bed, never after waking up
here's some juicy info
Supposed remedies
Note: Most of these have not been scientifically tested or reviewed in the above articles.
A glass of buttermilk. Though many people dislike buttermilk it will calm down your stomach and add liquid to your system. Tests have been done on monkeys and humans.
Having sexual relations may increase the release of endorphins, which in turn may help reduce the effect of a hangover.
Drinking coffee or other caffeinated beverages. Caffeine increases the effectiveness of analgesics, and therefore may reduce headache severity when used with aspirin or similar medicines. Coffee has also been shown in some studies to have a protective effect on the liver, effective in preventing alcoholic liver disease.
Nicotine, once again much like caffeine, increases the effectiveness of analgesics and its stimulant effects diminishes many hangover symptoms
Cabbage leaves or tomato juice
Mixing in a tall glass two raw eggs with pepper, tabasco sauce, and gin. Although the cysteine in the egg yolk may have a mild benefit, the pepper, tabasco, and gin will have a negative impact. Colloquially known as a "Prairie Oyster".
Drinking more alcohol (see hair of the dog), a well-liked, though misguided remedy.
Coca Cola or Pepsi-Cola, otherwise known as "Black Aspirin" (popular in Australia), also "The Red Ambulance" (Ireland); the caffeine, bubbles and sugar can be easier to hold down than pure water. Moreover, the low pH helps the enzymes in the stomach and the sucrose partially compensates the inhibition of the gluconeogenesis.
Taking a shower and oscillating between extreme cold and hot temperatures. This practice has no effect on the hangover and can be unhealthy. Seen in the movie The Princess Bride.
Eating canned asparagus before going to bed, purportedly a good cure thanks to the diuretic effects of asparagus. Again, diuretics compound the problem.
Ginseng tea is given to a drunkard to relieve the effects of alcohol. This may be the practice, but there is no reason to believe ginseng will help.
Eating whole jalapeños will help you awaken from a hangover.
Common folk medicine has a wide variety of supposed hangover cures. A good hangover cure should replace essential nutrients lost by the body while counteracting the influence of residual poisons; very few cures do both at once. Among the more common proposed cures are:
Drinking a sports drink such as Powerade or Gatorade, to re-hydrate and replenish lost nutrients in the body. Gatorade offers a high level of re-hydration and - if consumed before and after high amounts of drinking - can limit the effects of a hangover. Consumption of Vitamin Water, which contains high amounts of B vitamins and electrolytes often proves effective also. Pedialyte contains more electrolytes than almost any over-the-counter drug. This will help you re-hydrate your body as quickly as possible.
Drinking a large amount of water before going to bed, and during the night, for rehydration (a little water is much better than none).
Eating as much food as you can hold down. Your pyloric valve will shrink in response to the large amount of food you consume thereby reducing any further absorption of alcohol. A large meal is likely to contain nutrients to replenish your body and may also cause drowsiness which will help you sleep while your body repairs.
Eating mineral-rich foods, like pickles or canned fish
Drinking pickle juice, the solution in which cucumbers were pickled, in the morning (a staple hangover remedy in Russia and Poland). It is sometimes suggested to add honey to the solution.
Eating anything substantial, especially before going to bed, to "soak up" the alcohol in the stomach (e.g. a pizza, Doner Kebab or sandwich)
Orange juice, which is rich in vitamin C. However, the acidic qualities of orange juice can also make hangovers worse.
Taking a vitamin B1 (thiamin) supplement before going to bed
(instant) chicken or vegetable soup provides salt, proteins and electrolytes which help attenuate hangover symptoms
Drinking homemade Sauerkraut juice, the solution in which the cabbage was fermented in, in the morning (a staple hangover remedy in Serbia, called rasol)
Irn Bru is commonly regarded as a remedy in Scotland. It is believed that the high amount of sugar is the reason for this.
Cysteine, which is available as the over-the-counter supplement N-acetylcysteine (NAC), is known to assist in processing acetaldehyde, best taken while already drinking and/or before going to bed. (Egg yolk is also rich in cysteine, and it is notable that many hangover folk remedies or morning-after breakfasts incorporate eggs.)
Consumption of an Ulster Fry (popular in Northern Ireland), an Irish Breakfast or a Breakfast Roll, a meal that is an all day breakfast.
Day/night cold and flu tablets - Be wary of ones that contain paracetamol as it should not be mixed with alcohol. Both alcohol and paracetamol can affect the liver, but combined are worse.
Taking a dose of ibuprofen before sleeping can supposedly reduce hangover effects dramatically; however, the truth is that long term (longer than two weeks) use of ibuprofen increases the risk of stomach ulcers. Mixing ibuprofen and alcohol can cause stomach irritation and bleeding, and is highly recommended against. The adverse effects of alcohol are amplified when ibuprofen, which also can cause trouble with the liver, is taken with it. In fact, most medicines should not be taken with alcohol, so it is best to consult a medical professional before using this supposed "remedy".
Sleep. Some people argue that sleep only prolongs the negative effects of alcohol due to slower metabolism while asleep. However, others refute this by pointing out that one doesn't notice the negative effects of the hangover while asleep.
Exercise. Exercise can be painful with a hangover, but is usually very effective. It increases blood flow to the entire body, especially the head, and induces sweating, which helps the body purge alcohol. The feeling of lethargy dissipates and there is a strong mental and emotional effect where mood will improve.
Greasy food is a fairly effective remedy, though not as effective as "preemptive strikes" like the aforementioned Ibuprofen at night.
Going for a swim in cold water feels painful, but often helps to manage the headache.