It is narrated from Sayyiduna Thawban (may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings be upon him) said: "Three things do not break the fast: cupping, vomiting, and a wet dream; but the fasting person should not make himself vomit deliberately."
Hadith Referenceالمعجم الكبير للطبراني / باب الثاء / 1425