They’re protective covers that go over your drink and “protect” against someone trying to slip a Mickey Finn (or whatever they’re called these days):
The concept behind the cocktail cover is fairly simply. About the size of a coaster, it can be used to cap a drink that goes unattended. When a person returns to a beverage, there is a layer that can be pulled back, leaving a thin sheath protecting the cocktail. That can be punctured with a straw or pulled off entirely—either way the drinker will know that the cocktail has not been tampered with.
I’m sure there are many ways to defeat this security device if you’re so inclined: a syringe, affixing a new cover after you tamper with the drink, and so on. And this is exactly the sort of rare risk we’re likely to overreact to. But to me, the most interesting aspect of this story is the agenda. If these things become common, it won’t be because of security. It will be because of advertising:
Barry said that companies could advertise on the cocktail covers, likely covering the cost of production. Each cover, he said, costs less than 10 cents to make.