If they’re slow but somewhat durable I’ll put them on training bike/wheels and use them until they puncture. Or set them aside for that use whenever the current set wear out.
If I’ve already got a spare pair of training tires sitting around then I’ll give them away or sell them if I can be bothered with the hassle.
If they’re Mavic tires I’ll throw them away or give them to somebody I don’t like. Those guys appear to have no clue how to make a tire (and maybe not much more clue how to run a business judging by recent events).