I wouldn't feed those snack shacks, they're definitely bad. When rats chew on wood toys and such, they drop the wood. They don't ingest it, because they know it isn't food. The shacks are saturated in sugar and mollasses, so they think it is food, so they ingest it.
I don't freeze, I don't think it sanitizes them. I pour boiling water over them, and then bake them at 300 until dry. It prevents mites, parasites, insects, etc.