What is the ruling on a husband fondling his wife during the daytime in Ramadan and ejaculating without full awareness, and does this necessitate making up the fast or offering expiation?

You are not required to make up for the fast (qada') or offer expiation (kaffarah) for what you did, for two reasons: The first is that you were not mindful of fasting, so you are in the position of someone who forgot. The Prophet, peace and blessings be upon him, said: "Whoever eats or drinks forgetting, let him complete his fast, for it was Allah who fed him and gave him drink." The second is that you were ignorant of the ruling, which is that seminal emission due to foreplay is among the things that break the fast, and the ignorant person is excused. However, if you did that while mindful of fasting and aware of the ruling, then you have committed a grave sin, and you must repent and make up for the fast.