Is expiation obligatory upon the couple if the husband has intercourse with his wife during the daytime in Ramadan despite her refusal, claiming he could not control himself, and then drank water afterwards, and is the wife's fast invalidated in this situation?

Both of you must repent to Allah and make up the day. The expiation is binding upon your husband for engaging in intercourse during the daytime of Ramadan (definition). This expiation is the freeing of a slave; if he cannot find one, then fasting for two consecutive months; if he is unable to do that, then feeding sixty poor people. Your husband erred by eating after intercourse. As for you, the expiation is binding upon you if you were compliant and not coerced; otherwise, it is not.