The 'Urban Dictionary' defines a 'tactical vomit' as "the point in a night of heavy drinking where one forces themselves or chooses to throw up in order to feel well enough to continue drinking and keep up with the nights festivities - usually done after large amounts of drinking ...". Essentially this practice involves someone drinking too much and in an attempt to feel better or to sober themselves up they force themselves to vomit by sticking their fingers down their throat or by some other means, e.g., drinking a glass of salty water. So does this actually work and is it dangerous?
Firstly, it's incredibly important to remember that vomiting does not sober you up. The reason you are drunk and feeling unwell is not completely due to what is in your stomach - you are drunk because the alcohol has reached the brain. Emptying the contents of your stomach can reduce some of the toxins in your body and will certainly prevent anymore alcohol from reaching the brain and increasing intoxication levels but it certainly will not sober you up. So why do some people feel as if they have sobered up when they have thrown up?
When you vomit, putting the body under sudden and/or physical stress, endorphins and adrenaline are released. Endorphins are often described as the body's natural pain killers (or your 'own private narcotic'), and adrenaline boosts the supply of oxygen and glucose (energy) in your brain and muscles. This makes you feel pretty good (or at least a little better) for a short time. Unfortunately, your body does not keep releasing these chemicals and the effect wears off pretty quickly. If you combine this with the fact that by emptying the contents of your stomach you have decreased the amount of toxins (alcohol) in your body, vomiting may make you feel a little better for a short time but it certainly does not sober you up.
Making or forcing yourself to throw up is very different to the body's natural reaction to want to vomit. Tactical (or self-induced) vomiting after drinking alcohol is particularly problematic if it is done regularly, potentially causing damage in a number of ways. Most importantly, because you're trying to vomit up as much as you can you are likely to put far more strain on the esophagus (the muscular tube that connects your throat to your stomach), potentially leading to tears and bleeding. Adding to this is the combination of alcohol, stomach acid and food particles that travel across that area when you force yourself to vomit, all of which can get caught and cause inflammation and, in some case, lead to permanent changes.
Some people also report eye damage as a result of vomiting, waking up the next morning to find a part or all of the white of one of their eyes has turned bright red. This is called a subconjunctival haemorrhage and although it looks pretty terrible it's completely harmless. The haemorrhage is caused by an increase in pressure in the abdominal cavity that spreads to the blood vessels and causes the tiny vessels in the mucous membrane of the eye to burst. It can be caused by many things, including coughing, heavy lifting and even laughing, but forcing yourself to vomit can certainly do it.
So to answer your questions, yes, you may actually feel a little better straight after a tactical vomit but the effect isn't likely to last long and it certainly can't sober you up. Most importantly, never forget that vomiting can be life-threatening and when you force yourself to throw up there are increased risks.