Q: If the finger being was in the anus cavity just for cleaning purposes, will this break the fast?
A: If a dry finger is inserted and then removed, the fast will not break.
If a wet finger is inserted or after the dry finger was inserted, it was removed and the re-inserted, the fast will break and a Qadhaa of that fast will have to be kept.
This is the ruling, whether done knowingly or unknowingly.
Moulana Yusuf Laher