Third Party Bottle Caps

You can put a silicone cap on a beer bottle and stick it back in the fridge. There’s no law against it. You can drink oxidized, flat beer if that’s your thing.

Also, as reviewers have noted, if there’s carbonation left in your beer when you put one of these on, the pressure will pop the lid off, allowing your oxidized, flat beer to relax in your fridge uncovered.