[1] القئ vomiting: If one intentionally and deliberately draws vomit from the stomach (by sticking a finger down his throat, applying pressure to his stomach or deliberately smelling a repulsive odour) and it is a mouthful, the fast will be broken – there is a consensus upon this.

If the vomit was less than a mouthful, then Imām Muhammad’s R.A research is that it will still be broken. However, Imām Abū Yūsuf R.A says it will NOT be broken.

Ihtiyaat (caution) will be to take Imām Muhammad’s R.A opinion. Allāmah Aynī R.A writes:

الأصل فى العبادات الاحتياط” ”
وان إستقاء أى طلب القئ عامدا اى متذكرا لصومه ان كان ملأ الفم فسد بالإجماع مطلقا. وإن أقلّ لا عند الثانى وهو الصحيح لكن ظاهر الرواية كقول محمد انه يفسد كما فى الفتح عن الكافى.
وعن ابى هريرة رضى الله عنه قال قال رسول الله من ذرعه القئ
وهو صائم فليس عليه قضاء وان استقاء عمدا فليقض

If the vomiting was UNINTENTIONAL and without the person’s own doing, it does NOT break the fast, even if it was a mouthful.

If part of the vomit goes back down the throat, then if it went back down on its own, the fast is not broken. However, if it was deliberately swallowed, the fast is broken.

اذا قاء او استقاء ملء الفم او دونه وعاد بنفسه او اعاد
او اخرج فلا فطر على الاصح الا فى الاعادة

البناية ص 1400/ 2
شامى ص 393 / 3 تحفة ص 68
رواه الترمذى وابو داود. احكا رمضان ص 287
هندية ص 204 / 1 تحفة ص 66

Extracted from A Gift for Ramadhan, Page 51.

A Gift For Ramadhan – New 3rd Revised Edition