Sunan Abu Dawud
2380
Sahih+2

Narrated AbuHurayrah: The Prophet (ﷺ) said: if one has a sudden attack of vomiting while one is fasting, no atonement is required of him, but if he vomits intentionally he must make atonement

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid