I bought some bottled blueberries, and after eating most of them left the remainder in their liquid (a light syrup). After several months in the cupboard it's fizzy, alcoholic, and quite pleasant tasting... but is it safe to drink?
Wine will never spoil so that it is dangerous to humans, but that is assuming that it actually fermented to a decent alcohol level. Alcohol will kill most bacterias and preserve the liquid. However if the bottle was open, keep an eye out for bugs and other things that can have fallen into it. Baring that it should be perfectly safe to drink, or at least as safe as any liquid containing alcohol can be.