There are 7 things that will invalidate the fast: 1. Intercourse 2. Masturbation 3. Eating and drinking 4. Anything that is regarded as coming under the same heading as eating and drinking 5. Letting blood by means of cupping and the like 6. Vomiting deliberately 7. Menstruation and nifas

The view favored by Ibn Taymiyyah is that putting eye drops while fasting does not break your fast.

Emission of madhiy does not break the fast according to the more correct of the two scholarly opinions whether that is because of kissing one's wife, watching movies, or other things that provoke desire.

There is strong evidence for the view that the one who eats or drinks after Fajr or sunrise by mistake, his fast is valid and he does not have to make it up. However, it is better for him to fast a day later.

If a man falls into a coma in Ramadan for the entire day – i.e., from dawn until sunset – his fast is not valid, and he has to make up the fasts he missed. If he was awake for part of the day, then his fast is valid.

Smoking is haram whether in Ramadan or outside Ramadan. Smoking invalidates the fasting because the smoke contains particles that reach the stomach

If the injection provides nourishment that takes the place of food and drink; it breaks the fast because it is like eating and drinking. If the injection is not a kind of nourishment; this does not break the fast.

The correct scholarly view is that masturbation is haram. But masturbation at night in Ramadan does not invalidate your fast, either on the day before or the day after.