Are you allowed to rinse your mouth with mouthwash after אפיקומן
You should not rinse your mouth with mouthwash after afikoman. The reason we don’t eat after afikoman is in order that the taste of the matzoh should stay in our mouth. The purp[ose of mouthwash it to clear the mouth of any other taste and exchange it with the mint flavor. Therefore it shouldn’t be used.
Kovetz Halachos (Pesach) 32-15