Is the waiter making a smart or a nasty suggestion?
(Even granting the presupposition that people would love to have some Limburger but normally refrain from concern about offensive breath.)
1) Now is the chance, as customers are masked and will be protected from others noticing their bad breath the rest of the day. So the waiter is making a good suggestion.
OR 2) But actually he is leading them on, knowing that a masked person will be smelling their own breath all day. So he is nasty and taking out some revenge on customers.