Can Coffee Help You Sober Up?

Nope, not really:

[C]affeine can counteract the tiredness induced by alcohol, which might explain why a cup of coffee is popular in many places at the end of a meal. But it can’t remove feelings of drunkenness or some of the cognitive deficits alcohol causes. … It takes approximately an hour for the body to metabolise one unit of alcohol, although some people do it faster and some slower, depending on their genetic make-up, how much food they’ve eaten and how often they drink. Caffeine doesn’t speed up the process. However its effects vary according to which function you’re looking at. One study, for example, found a large dose of caffeine can counteract the negative effects of alcohol on memory, but that feelings of dizziness remain.

There are also suggestions that caffeine can make matters worse. If you feel tired you are more likely to realise that you must be drunk, but if the caffeine takes away some of that fatigue you might believe you’re sober when you’re not.