Answer
In the following situations, both qadha and Kaffarah become obligatory, provided these acts are committed intentionally, voluntarily and without any force or pressure, during the fasts of Ramadhan:
1. Eating
2. Drinking
3. Sexual Intercourse
4. Masturbation
5. Staying in the state of Janabat till the time of Fajr prayers
And as a recommended precaution, invalidating the fast due to reasons other than those mentioned above, should also be recompensed with Kaffarah, besides the obligatory qadha .