The smell in the bathroom is often due to sewage or mold. Therefore, it is important to deal with the root cause of bad breath.
If there is a smell of dampness in the room, it means that mold is hiding somewhere. As a rule, it occurs in the bathroom, toilet or kitchen, as well as in places where there is water: for example, near a cat's water bowl.
Take a glass of plain table salt and pour it into the drain hole in the sink. Boil the kettle and pour half a liter of boiling water into the same hole. Wait 2.5 - 3 hours and turn on hot water to rinse out the residue. Salt has good cleaning properties and corrodes grease and dirt in the siphon.
So, here is a list of work that should be done to eliminate the unpleasant smell of sewerage: replace flanged and water pipes; take measures to drain and waterproof the floor; make repairs indoors using waterproofing materials not only on the floor, but also on the walls.