Is it permissible for me to break my fast if I sleep through the suhoor while observing a fast for an expiation of an oath?

A Muslim is not permitted to break a mandatory expiatory fast without a legitimate Shari excuse. If you are able to complete the fast without unbearable hardship, then you have no dispensation to break it. However, if the fast causes you unbearable hardship, you are permitted to break it, but it is more cautious to restart the fast from the beginning. It should be noted that fasting as an expiation for an oath is only resorted to when one is unable to feed, clothe, or free a slave.