Reference: Fataawa Ramadhaan – Volume 2, Page 481, Fatwa No. 424
Question: What is the ruling of one who vomits whilst fasting, does he have to make up his fast or not?
Response: It’s ruling is that he does not have to make it up. As for the one who intentionally vomits, then he must make up his fast, as the Prophet (sal-Allaahu ‘alayhi wa sallam) said:
«One who vomits, then he does not have to make it up, and he who intentionally vomits, then he has to make it up». Transmitted by Imaam Ahmad and the four Imaams of the Sunan (Aboo Daawood, at-Tirmidhee, an-Nasaa’ee and ibn Maajah) with a Saheeh chain of narration on the authority of Aboo Hurayrah.