If the fasting Person has sex with his Wife and he forces her to do so against her will
Question :
If a man has sex with his wife in the daytime during the fast and he forced the wife to do that, and they are not able to free a slave or fast due to their being busy seeking livelihood, is it sufficient for them to give food? And what is the amount and type of food they must give?
Answer:
If the man forces his wife to have sex while they are both fasting, then the fast of the woman is correct and there is no expiation on her. However, the man is obligated to make expiation for the sex that he had if that occurred during the daytime of Ramadhan. The expiation is freeing a slave. If he cannot find a slave, then he must fast two months consecutively. If he is not able to do that, he must feed 60 poor people, due to the Hadith of Abu Hurairah that is recorded in the two Sahihs (of Al-Bukhari and Muslim). He must also make up for the day of fasting.
Source:
Ash-Shaykh Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 3 Page 280