Shaykh Ibn Uthaymeen was asked:
“If a person vomits – may Allah honor you – some traces of clear food are apparent in the vomit. So is it allowed for him to vomit in the toilet?”
“Yes. If vomit comes out from the stomach, then it is impure according to many of the scholars or majority of the scholars. So like this, there is no harm to vomit in the toilet even if some mass of food is present. However, it is impure according to the majority of the scholars. Also, according to the opinion that it is pure, it still does not have sanctity. So like this, the Prophet (ﷺ) mentioned vomit in the position of dispraise. He said:
العائد في هبته كالكلب يقيء ثم يعود في قيئه
One who gets back his gift is like a dog which vomits and then swallows that vomit.
[Saheeh Muslim no. 1622]
So he made this something repulsive”. End translation. [Liqaa al-Bab al-Maftooh no. 130]
Faisal Ibn Abdul Qaadir Ibn Hassan