Vomiting can be a symptom of dehydration. You couple the body's toxin response from the booze with the dehydration caused by the booze, and this can lead to vomiting. In fact, most classic hangover symptoms are dehydration symptoms.

The first place your body starts to absorb alcohol is through your mouth, especially under your tongue. You, of course, absorb alcohol through your stomach as well. The highest rate of alcohol absorption happens in the small intestines, however. This is why your blood alcohol level continues to go up well after your last drink.

Our bodies can process, on average, one serving of alcohol per hour. The serving size depends on the alcohol by volume of the specific drink, the person's biological sex, and the person's weight. If you drink more than your body can process, it begins to build up in your blood stream and cause intoxication. Once it is in your blood stream you are at your body's mercy to process it. There is no real, effective trick to "sober up". Tactics may make you feel more alert, but your BAC won't change. Food won't help, coffee won't help, and slamming water won't help speed this process up.

Basically, unless you've chugged a bunch of alcohol in a very short amount of time, vomiting won't save you. By the time you feel nauseous, the damage is already done. Your body has absorbed and is processing the alcohol you already drank.