There is also a rather rare medical condition where a person lacks the enzymes needed to properly break down sugars, the resulting partial breakdown being alcohol as a byproduct. Children born with this defective gene often become alcoholics before they are able to talk as the parent has little idea of what's going on until the child falls behind in the motor skill development curve. I wish I could remember the name of the disease, but it's really a rather nasty one. The only treatment is via a very very low sugar diet.
Again, this is an incredibly rare disease though.