1 Tbsp ACV mixed with 1 Tbsp honey and about 4 oz water works great for acid reflux/GERD. Often when we have acid reflux, we need more acid, not less, which is why acid reducers often don't work.
I've read that ACV is good to help burn fat, as well, but I've never been consistent enough with it, so can't vouch for that.
I have been using ACV and mineral water mix as a toner on my face. I use about 1 part vinegar and 3 parts mineral water or just plain water works too. I have been working out a lot and that normally gives me acne, but much less with the ACV/mineral water mix. Also I read on Pinterest that if you take 3 Tablespoon of ACV it helps burn fat, so I'm doing that too, but also eating well and exercising, so no proof if ACV works for that! It is also supposed to be helpful for heartburn, but I don't have that. Cheers