You could sell apks

Yes, but you don't sell it directly to Cuba, you sell it to $COUNTRY which might eventually sell it to Cuba (and you don't even know about it)

It's not you selling to Cuba, it's Cuba buying through intermediates.

(Of course if you really want you can sell things directly to Cuba, but you need to find a way of disguising it)

You're (or, were) also forbidden from bringing Cuban cigars to the US, but if you arrive from a flight from Panama with a box of unmarked cigars nobody is going to do anything.