Is there any way to prevent bad breath if someone has gastroesophageal reflux disease?

Try parsley oil: If your bad breath is being caused strictly by your reflux disease then make sure you are taking some type of acid reducer like Prilosec and you can try going to a health food store and ask them about parsley oil supplements for the breath problem. Also make sure you have good oral hygiene and don't forget to brush your tongue or use a tongue scraper.

Treat the GERD: In addition to treating the gerd you may want to try smart mouth oral rinse as it binds sulphur compounds that are a major former of gases that contribute to bad breath. Also brush with a toothpaste containing bicarbonate (sodium bicarbonate) to neutralize oral acids that form from the dissolving of the hydrochloric stomach acid gas in the saliva. Bicarbonate (sodium bicarbonate) oral rinses may also help breath & tooth problems from gerd.