Acts which break the fast
By Mufti Muhammad

To eat or drink mistakenly
A person knows he is fasting, mistakenly eats or drinks something, or is compelled to eat. A person knew he was fasting but while rinsing his mouth or nose, some water went down his throat, or someone poured some water in his mouth while he was sleeping and he drank it, or he was forced to eat or to have sexual intercourse that is, he was threatened that if he would not break his fast he would be killed or lose one of his organs, or to suffer some misfortune, so the person broke his fast; or he forgetfully ate or drank something or had sexual intercourse, or he discharged during the day, or during storke of a sexual eye he discharged, or he vomited, in all these cases he thought that his fast had been broken so he ate or drank something intentionally, his fast will now break and it will be fardh (necessary) upon him to keep its qadha only.

Only two conditions of vomiting break the fast
There are different forms of vomits, only two of which break a fast. One is that a person vomited a mouthful intentionally, and either threw it out or swallowed it back, in either case his fast will be lost. The other form is that he vomited a mouthful unintentionally but he swallowed it down intentionally. So if it was equal to a chickpea, the fast will break. In both these cases only qadha is wajib but only if he is aware of his fast while vomiting and the vomit is in the form of food, water blood or bile. The swallowing of phlegm doesn't break a fast in any condition.

Except for these two forms of vomiting the fast doesn't break in any other condition. For example, a person vomited intentionally but it was not a mouthful, or he vomited unintentionally but not a mouthful, or the vomit was a mouthful but it was not swallowed down the throat, either it was thrown out or swallowed unintentionally but it was less in amount to a chick pea, or he vomited a mouthful intentionally or he vomited a mouthful unintentionally and swallowed it down but he did not remember he was fasting, then the fast will not break in all these cases.
(Raddul Muhtar Pg.414, Vol.2)

If a person vomits intentionally again and again in one place and it equals to a mouthful of vomit then the fast breaks. If the total amount is less than a mouthful or he vomited in different places the fast will not break.
(Fath-ul-Qadeer)


Cases in which even if the fast breaks, eating and drinking is not permissible until sunset
A person took a sahri on the assumption that it was not dawn yet but the day had actually dawned, or a person broke his fast on the assumption that the sun had set, but the sun had not actually set, or a traveler returned back from his journey during the day time, or a woman's menses or nifas was over during the day, or a person recovered from madness during the day, or someone's fast broke either he was forced to break it or water etc. went down his throat, or a Kafir accepted Islam during the day, or a person reached the age of puberty during the day, in all these cases its wajib upon these people to pass the rest of their day like normal fasting persons. Except for the last two persons i.e the new Muslim and the newly mature, qadah is also wajib on all the other persons. If these two persons, the new Muslim and the newly mature, had made intention of fasting before midday, then their fast will be considered as a fardh. But if a woman's menses are over after subh-i-sadiq and she makes the intention of fasting then her fast will not be counted, neither as fardh nor nafl.
(Al-Bahr Pg288, Vol.2, Raddul Muhtar Pg47, Vol.2)