What is the ruling on some perfume entering the mouth of a fasting person unintentionally, and what is the ruling on fasting to make up for doubt concerning the validity of the Ramadan fast?

Using perfumes and smelling them does not break the fast of a fasting person. If a fasting person swallows some perfume unintentionally, it does not harm him. The fast is only broken by certainty of consuming something that breaks the fast. Mere doubt does not invalidate the fast.