Made juice from pineapple skins and let it sit in my fridge sealed for a long ass time. I opened it today, expecting it to be trash, but to my surprise it was totally fine. Assuming that the yeast from the pineapple skin kicked in. Pretty damn tasty too. 10/10, would recommend, although I'd recommend actually doing this intentionally
Methanol pretty much only comes from distillation, or cutting something with industrial-grade alcohol. If you're fermenting apple juice there might be a tiny amount of methanol, enough to give you a hangover but not enough to make you go blind.
You can just add yeast to a jug of apple juice and let it sit with the cap on loose for a week or two and it will make something with alcohol in it, but if you want it to consistently taste good there's a little bit more involved. Still, it's one of the easiest ways to make your own booze.
Here's a more detailed guide: https://howtomakehardcider.com/