My husband recommends coffee grounds (unused ones). He drove semi truck years ago and when he would have to haul something that had a bad odor and it lingered in the van trailer. He would dump a can of coffee in it and shut the doors and in a couple days all the smell was gone. Of course, the price of coffee was a lot less in those days. Don't let the coffee get on the fabric, but just put some in a bowl in the box with the fabric and shut the box for a few days and see what happens.