I recall a cabin crew announcement shortly after take off on a flight from LHR to OSL:
"Any passenger found smoking will be asked to leave the flight immediately"
Not practical, but it got the message across.
A requirement to declare face mask exemption, with supporting documentation, prior to check-in seems quite reasonable. And if anyone claims that they are still drinking, provide them with a straw. Although there is precedent in song for that leading to the acquisition of a mother-in-law (but possibly only if the drink is cider).