Vomiting does not break the fast. What breaks the fast is eating, drinking and sexual intercourse. According to a narration, it is said that “Fasting is refraining from what goes inside the body, not from what comes out of it”.
The books of Islamic Law say that vomiting on purpose will break the fast, but vomiting involuntarily will not. The following narration is shown as evidence:
“The Messenger of Allah said: A person who vomits involuntarily while fasting does not need to fast once again. But if he vomits intentionally, he should fast one more time.”
Tirmidhi says the following about this narration:
“This narration is neither weak nor strong. We only know this from the narration of Isa ibn Yunus from Hisham ibn Sirin from Abu Hurairah.”
Bukhari says the following about this narration:
“This narration comes by different syntax from Abu Hurairah and it does not have a strong ground. It is also narrated that the Messenger of Allah broke his fast by vomiting. The story was like this: The Messenger was fasting. He vomited and did not carry on fasting since he became weak and powerless.”
When we look upon the verses regarding fast, we see no reason to think that vomiting will break the fast.