Consider an alternative theory: the vinegar is a digestive aid (just like pineapple) and your root cause or part of it is, in fact, indigestion. I only suggest this because I found indigestion to be the one and only consistent cause to heartburn/reflux in myself. Seems like some foods don’t want to break down from normal stomach acid but will respond to other acids. So that’s my theory. But whether it’s accurate or not, it does work.