Dorota,Your question is an important one.  Apple Cider Vinegar (ACV) is powerful for helping with athritis, it cleanses the blood and in stark contrast to your experience it helps people with acid reflux! Read my article on ACV to learn why.Other than giving yourself smaller doses and allowing your body to build tolerance to it, adding water (8 -12 ounces) to a tablespoon of ACV can make drinking it easier and dilute the acidity that is causing your stomach ache.Try this method and if it still causes issue then use less ACV and drink it more often.I hope that this works Dorota. My mother has RA and together we have kept her drug free for a decade!!Happy Drinkin!Yours in health and living life to your fullest, Dr. Malik