Have you ever accused your friend of drinking, seeing their condition, and lab tests and your friend do not admit it? There is a few percent chance that he or she might be true. There is a syndrome called Auto-Brewery Syndrome.
In this syndrome, ethanol is literally produced inside your body, either your urinary tract, oral cavity, or any other part of the gastrointestinal tract. As to some of you, it might seem a boon, as the internal factory is set for alcohol, but it has serious consequences.