Mishkat al-Masabih #1916

He reported God’s messenger as saying, "If one has a sudden attack of vomiting while he is fasting no atonement is required of him, but if he vomits intentionally he must make atonement." Tirmidhi, Abu Dawud, Ibn Majah and Darimi transmitted it. Tirmidhi said this is a gharib tradition which he knew only among the traditions of ‘Isa. b. Yunus, and that Muhammad, i.e. Bukhari, said he did not consider it one which was held in estimation.