VK's Channel shared a video in which a one millimeter piece of cardboard is applied inside a Joy-Con experiencing drift issues.
Nintendo is aware of the problem, and fixes the issue for free, but for those that don't want to send in their Joy-Con to have it fixed, this could be an elegant solution!
Now, it's worth noting that I have not personally tried this method, and opening up the Joy-Con controller will likely void Nintendo's warranty.
For those unfamiliar with Joy-Con Drift, it's an issue where the Joy-Con controller reacts as if the user were pushing the control stick, but no actual pressure is being placed!