I saw what I thought was a silly idea sitting on a customers counter top until I saw first hand how good it worked.
He had used two plastic cups, poked a hole in the bottom of one of them the size of a pencil.
Dropped a slice of an apple in the other one.
Then he just taped the to together top to top.
They could find there way in, but not out.
Once it had done it's job he just taped over the hole and tossed the whole thing in the trash.