ACTS THAT DO NOT BREAK YOUR FAST

• If a fasting person forgetfully eats, drinks or has sexual intercourse, the fast will not break. If he eats and drinks a full-stomach, even then the fast will not break. If he forgetfully eats or drinks several times in the day, the fast will still not break.
• A person slept away during the day. He saw a dream which made ghusl compulsory on him. (i.e. he had a wet-dream) In such a case, the fast does not break.
• During the day, it is permissible to apply surmah (antimony), oil, and to inhale any fragrance. The fast is not affected by such acts irrespective of when this is done.
• It is permissible for a man to sleep next to his wife, to touch her and to kiss her. However, if, due to the passions of youth, there is the fear that these acts would lead to sexual intercourse, they should be abstained from.
• A fibre of meat or fragments of food etc. was stuck in the teeth. If it went down the throat on its own and if this fibre is less than the size of a gram-seed, the fast will not break.
• By swallowing one's saliva, the fast does not break irrespective of the amount swallowed.
• Ghusl became compulsory at night. However, the person did not have a bath and only took a bath during the day. The fast will be valid. In fact, even if he does not bath the entire day, the fast will still be valid. However, he will still be sinning for not bathing.
• If a person puts water in his ears, the fast will not break.
• If a person tastes something with his mouth and thereafter spits it out, the fast will not break. However, it is makruh to do so unnecessarily. But if one's husband is very hot-tempered and there is the fear that if the salt or water content in the gravy is not in order, he will become extremely angry, it will be permissible to taste and will no longer be makruh.
• It is makruh to soften any food with one's mouth and feed it to a child. However, if this becomes necessary and there is no alternative, it will not be makruh.
• Injections do not invalidate the fast.
• Backbiting although haram and a grave sin does not invalidate the fast but should be avoided.
• Use of musical instruments, although a grave sin, does not invalidate the fast but should be avoided.

ACTS THAT DO BREAK YOUR FAST

•  Incense sticks were burnt and the person went and sat near them and inhaled the smoke. The fast will break. In the same way, the fast breaks by smoking cigarettes, cigars, etc. Apart from this smoke, it is permissible to inhale the fragrance of perfumes which do not have any smoke.
• A fibre of meat or fragments of betel-leaf, etc. was stuck in the teeth. Due to cleansing the teeth, this fibre released itself from in between the teeth and the person ate it. However, he did not remove it from his mouth. It went down his throat on its own. If it is equal to or more than the size of a gram-seed, the fast will break. However, if the person removed this fibre from his mouth and thereafter swallowed it, his fast will break irrespective of whether it was smaller or larger than a gram-seed. In both cases the fast will break.
• While rinsing the mouth, water went down the throat and the person knew that he was fasting. His fast will break, qada will be wajib, but there will be no kaffarah on him.
• A person vomitted unintentionally. The fast will not break irrespective of the amount. However, if he vomitted intentionally, his fast will break if the vomit was a full-mouth.
• If a small amount of vomit came out and it was swallowed intentionally the fast will break.
• When a person has sexual intercourse, the fast will break, qada will become wajib, and it will also be wajib to observe kaffarah. Once the head of the penis enters the vagina, the fast breaks and qada and kaffarah become wajib. This is irrespective of whether ejaculation takes place or not.
• While fasting, a person took snuff, put some oil in his ears or took an enema without taking any medicine orally. The fast will break. However, only qada will be wajib and not kaffarah.
• While fasting, it is not permissible for a woman to insert any medicine, oil, etc. in her vagina. If she inserts any medicine into the vagina, the fast will break, qada will be wajib but not kaffarah.
• Blood comes out from the mouth where its quantity is equal or more than the saliva. It is then swallowed together with saliva. The fast will break.
• It is makruh to cleanse the teeth with coal or tooth-powder. If any of these things go down the throat, the fast will break. It is permissible to clean the teeth with a miswaak. This is irrespective of whether it is a dry miswaak or a fresh one. If the miswaak is obtained from the neem (margosa) tree and one perceives it's bitterness in the mouth, even then it will not be makruh to use such a miswaak.
• A person ate something forgetfully and thought that since he has eaten, his fast is now broken. He therefore ate something intentionally. His fast will now break, qada will be wajib on him, but not kaffarah.
• A person vomited involuntarily and thought that his fast is now broken. He therefore consumed some food. His fast will break, qada will be wajib, and not kaffarah.
• A person applied surmah, underwent blood-letting or applied some oil and thereafter thought that his fast has broken because of any of these causes. He therefore ate some food intentionally. In this case, both qada and kaffarah will be wajib on him.
• A woman begins to menstruate during the fast. The fast breaks and qada becomes wajib.

I do hope i have been able to clarify a few details and enlighten ourselves. There is always something new to learn in Islam. May Almighty Allah make it easy for us to understand and practice. Ma Salam.

NB; Reference was made to works by  Ebrahim Saifuddin and Muhammad Mustafa Azmi.