Don't be afraid to let your dog be messy!
Try using items like cardboard boxes, paper egg cartons, or the cores of paper towels as food-carrier toys. They can provide loads of fun for dogs. Simply add some treats or your dog's meal to one of the homemade toys, close it up (use a small piece of masking tape), and hand it to your dog to tear and shred!
Another idea is to repurpose any leftover plastic jars. Add peanut butter, wet dog food, almond butter, etc. to the inside and bottom of the jar to create a fun activity for your dog that will keep him or her busy for awhile.
Of course, supervise your dog with any of these creative toys!