I have a problem in my stomach that makes food come back up when I have some liquid in the mouth, and this happened in Ramadan. Do I have to make up that day?
Praise be to Allaah.
If something comes back up out of the stomach into the mouth, then the fasting person must spit it out; if he deliberately swallows it, his fast is invalidated, but if he swallows it without meaning to, he does not have to do anything.
Standing Committee for Academic Research and Issuing Fatwas
Fataawa al-Lajnah al-Daaâimah - vol. 2 (9/211)
-- Islam QA