Does Unintentional Vomiting Break Your Fast?
Question

I fasted six days of Shawwal and the fifth day was a Friday. At the time of Fajr prayer, I unintentionally vomited what I had eaten, but I completed my fast and fasted on Saturday too. Is my fast valid or invalid?
Praise be to Allah.Your fast is valid, and the fact that you vomited does not matter, because if a person vomits unintentionally and without meaning to do so, his fast is still valid. But the one who vomits intentionally has broken his fast. Al-Tirmidhi (720) narrated from Abu Hurayrah (may Allah be pleased with him), that the Prophet (peace and blessings of Allah be upon him) said: “The one who cannot help vomiting does not have to make up the fast, but the one who vomits deliberately has to make it up.” (Classed as sahih by al-Albani in Sahih al-Tirmidhi) 
Ibn Qudamah (may Allah have mercy on him) said in al-Mughni (3/23): 
“The one who makes himself vomit has to make up (the fast), but the one who cannot help vomiting does not have to do anything . 
What is meant by making oneself vomit is vomiting deliberately, and what is meant by “cannot help vomiting” is when it happens involuntarily . The one who makes himself vomit has to make up the fast because his fast has been spoiled, but the one who cannot help it does not have to do anything. This is the view of the majority of scholars. Al-Khattabi said: I do not know of any difference of opinion among the scholars.”
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) was asked about vomiting in Ramadan – does it break the fast?  
He replied: 
“If a person vomits deliberately then it breaks the fast, but if he vomits unintentionally then it does not break the fast. The evidence for that is the hadith of Abu Hurayrah (may Allah be pleased with him) … and he quoted the hadith that we have quoted above. 
If you could not help vomiting , then you did not break the fast. If a person feels that his stomach is queasy and that its contents will be expelled, do we say that you have to try to stop it? No. Or that you have to make it happen? No. Rather we say: Take a middle approach – do not make yourself vomit and do not try to stop it, because if you make yourself vomit you will break the fast, but if you try to stop it, that will harm you. So leave it, and if it comes out without any action on your part, then it will not matter and that will not break your fast.” (Fatawa al-Siyam, p. 231)
And Allah knows best.