What is best for an upset stomach: pepto bismol liquid, mylanta one dose chewable tablets, or alka-seltzer extra strength heartburn relief chews? i already tried maalox and tums?

Any of these will do Generally the first two work well. But if your symptoms are recurrent pl see your doc.

If those are your only options, I would try the Pepto-Bismol next. It mostly depends on what your symptoms are, and what you mean by an upset stomach. The Mylanta works in a similar manner to mailbox at times, so you have already tried that. I would avoid the Alka-Seltzer if it contains aspirin. If your symptoms are persistent, see your doctor. Good luck.