So I have heard about a fairly rare condition called auto-brewery syndrome. In reading medical articles about it, it wasn't really too clear exactly how it happened other than there are rare fungus or bacteria that can get into a person's gut and somehow ferment alcohol. Finally read a news article that really made one case very simple to understand.
A guy in his 40s had symptoms of dizziness, brain fog and unusual aggression so he goes to the doctor. Doctor thinks he has depression or something of that nature and puts him on anti-depressants.
He continues to have these symptoms and gets pulled over and is suspected of DUI. The guy is adamant he didn't have any alcohol to drink but tests positive for a BAC that is about 20 drinks worth!
Luckily his aunt had heard of something similar and has him checked out in more detail and surprise surprise - doctors find a fungus in his gut that converts carbohydrates into alcohol. It took a while and a few different treatments because after the initial round of anti-biotics, the fungus had moved to another part of his digestive tract so it took another round of new treatments but eventually, after years and years of the condition, he returned to normal.