Vomiting while Fasting
Abu Hurayrah (radiyallāhu ‘anhu) narrated that Allah’s Messenger (salallāhu ‘alaihi wasallam) said: “Whoever has a sudden attack of vomiting does not need to make up the fast but whoever vomits deliberately must make it up.”
Vomiting is to vacate the stomach by way of the mouth. And if this occurs without one’s own choice so that he is overtaken by it, then it does not harm his fast. However, if he causes himself to vomit by inserting something into the back of his throat such as his finger, then his fast is broken.
 Ahmad in Al-Musnad (no. 10463), Abu Dawūd (no. 2380), Ibn Mājah (no. 1676), At-Tirmidhi (no. 720), An-Nasā’ī in Al-Kubrā (no. 3130) and declared to be sahīh by Al-Albāni, see Al-Irwā (4/51). See also Tas’hīl al-Ilmām of Shaikh Al-Fawzān (vol. 3).