One thing that strikes me about the story- I guess not everyone is queasy about putting things in their ears that have spent a lot of time in another person’s ears? (I wouldn’t think they would be attractive theft targets, because of hygiene/stigma)
Like I said, it’s queasiness/stigma about hygiene, not a reasoned thought. This is a common sentiment in the US- we like to buy our sex toys new, for another example, even though they’re usually made of materials that lend themselves to cleaning/sterilization.
I’d leave ‘em in the sun personally.
But putting it random stuff at the edge of your ear is probably low risk when it comes to activities people do on the regular.
There's also a device which bombards small device like earphones with UV for a couple of minutes. Got it at work. My over ear headphones don't fit, but my Sony in-ear with noise cancelling do. Oh, and they still work afterwards, of course.