But they don't. The only "drunk" trait coffee can counteract is the tired, foggy feeling. So drinking coffee when you're drunk just makes you a judgment-impaired, over-confident, dehydrated, uncoordinated and very awake drunk person [source: Discovery].
Which would probably be fine except that adding "very awake" into the equation can make a drunk person feel less drunk -- thus making driving a car, operating a backhoe or chopping some vegetables seem like perfectly reasonable propositions.
Next, a happy one!