... On the fourth day, I noticed that the container (a plastic milk jug) was bowed outwards. When I popped the cap, air escaped (presumably CO_2). The juice was carbonated and a bit sweeter than I remembered. It tasted good.

This stuff is perfectly safe to drink, right? No bad alcohols (methanol) form during natural fermentation, right?

I know bad stuff can happen when you're making hard liquor. And I seem to remember hearing that bad stuff can happen when juice is not pasteurized (at least in the context of cider), but that's nothing to do with the fermentation process, right?

Thanks for your thoughts.

EDIT: I drank it. Still alive