To make old toys seem new to your dog, rotate them regularly, so they don't get bored with the same ones. Hide some toys for a few weeks, then reintroduce them later, as this can rekindle your dog's interest. Adding a fresh scent by rubbing a small amount of dog-safe flavoring, like peanut butter or chicken broth, can make old toys more exciting. Additionally, interactive play, such as stuffing toys with treats or using puzzle toys, can mentally stimulate your dog, making the toy feel like a new challenge.