Coffee can be quite acidic which with people with overactive stomachs can cause issues such as acid reflex, ulcer etc. Instant coffee tends not to be as acidic

Coffee can be quite acidic which with people with overactive stomachs can cause issues such as acid reflex, ulcer etc. Instant coffee tends not to be as acidic same goes for cold brews and there are other ways to neutralize the acidity. If you produce too much acid then intermediate fasting is not a good idea to begin with unless you also take supplements to control your stomach acidity.