Since everyone else has done the hard work of saying something insane, I'll be the only guy in the entire fediverse who throws inedible rocks in the garbage.
I'd like to, but I'm not constantly getting up to throw them in a bin at a crowded theater. If I had a bag or smaller container to put them I would hold them to throw when leaving but I can't think of a time I was that prepared...
Ahh I get it. This is a zero G issue. Planetside, kernels fall conveniently to the bottom of the receptacle for disposal at a convenient time. I now see how this isn't a completely universal and obvious solution.
Maybe if you chew some gum on the way to the theater, you can stick it to the side of your popcorn tub and attach any unpopped kernels to it as you go. That would also prevent them from floating into the projection beam!