There are hard rubber toys that have holes in them so you can poke treats inside and, theoretically, the dog plays with them in hopes of getting the treats back out again. Personally, I think it's a little frustrating to the dog. In my experience, dogs just sleep if their owner isn't home, even if other people are around. My dog has company during much of the day, but except for when people come in, go out or eat (or the mailman comes), she mostly just curls up and sleeps till I come home. If there's no one home to monitor and your dog's being destructive, crating probably is the best solution, at least while he's still young enough to be full of it.