I've read that one issue is insufficient acidity in the stomach, so the valve at the top isn't closing properly. The low acid could be from antacids or a low sodium diet (which means a low chloride diet - and I think we need that for hydrochloric acid).

One solution that seems to work at least for some folks is consuming something acidic, like cider vinegar or wine vinegar mixed in water.

I can't vouch for any of this (not even n=1) as I don't suffer this problem, but I have developed a taste for 'haymaker's punch' (apple cider vinegar and optionally molasses mixed into water) - and I can tell you that drinking a lot of this does not give me reflux, so it's likely worth a try.

FWIW, I switched to this for post-workout right after they turned Gatorade into a kind of soda, maybe a decade or two ago. That punch (often called 'Switchell') is an old-time traditional drink here in New England for farm workers out sweating in the hot sun.

Trivia: The Roman legionnaires, when on march, often drank water with vinegar mixed in. Dunno if that was for taste, an attempt at water purification, or not getting sick from sweating a lot.