Rules regarding things which invalidate a Fast

1662. If a person intentionally and voluntarily commits an act which invalidates fast, his fast becomes void, but if he does not commit such an act intentionally, there is no harm in it (i.e. his fast is valid). However, if a person in Janabat sleeps and does not do Ghusl till the time of Fajr prayers, as detailed in rule no. 1639, his fast is void.
Similarly, if a person due to utter ignorance of the rule that a certain act will invalidate the fast, or due to reliance upon some authority which he thought was genuine, unhesitatingly commits an act which invalidates the fast, his fast will not be void, except in the cases of eating, drinking and sexual intercourse.

1663. If a fasting person forgetfully commits an act which invalidates fast and thinking that since his fast has become void, commits intentionally another act which invalidates fast, his fast will be void.

1664. If something is dropped forcibly down the throat of a fasting person, his fast does not become void. But, if he is compelled to break his fast by intimidation, like, if he is warned that his life or wealth would be at stake, and he willingly breaks the fast to ward off the danger, his fast will be void.

1665. A fasting person should not go to a place where he knows that something will be put down his throat or that he will be compelled to break his fast by his own hands. And if he goes there and he is compelled to commit an act by his own hands which invalidates a fast, his fast will be void. The same will apply, as an obligatory precaution, if something is forcibly put down his throat.