There are several studies showing that “inspiratory muscle training” can be effective for GERD. Basically you train by breathing in through small device that makes it harder to inhale, and that strengthens your esophageal sphincter.

I did this for some time and anecdotally I do believe it helped me. There are several studies showing it to be effective, but the big caveat is most if not all of these studies were small and were funded by PowerBreathe, the company that manufactures these devices.