Definitely would NOT put bleach in the mop. It is most definitely corrosive to any metals and plastic. You also will likely void your warranty as they all instruct you to not put anything in the reservoir except water (you do use only distiller water, right). That being said, since vinegar is used in irons and coffee makers to clean THEM, I would venture a guess that a few DROPS of white vinegar in the reservoir would prevent any bacterial growth and smell without causing damage to the unit.