Kong Stuffing Possibilities?

We fostered a Pointer who went to a fantastic forever home where the new owners smear a layer of cream cheese and peanut er inside the Kong and freeze it. That keeps them busy for awhile. We have the largest size Kongs for our Great Danes. Each dog has their own and we don't typically freeze them. We have, on occasion, frozen water with fruit slices in small stainless steel bowls for them to lick and play with. We also smear a bit of peanut er in their Kongs as a special treat, but not too often. We don't stuff the entire inside full, just a coating around the inside. You could try doing apple sauce, just the plain, unsweetened variety. You could mix apple sauce with some plain yogurt and freeze it inside the Kong. You could make a fruit puree in a food processor with some blueberries, banana and apple and mix that with yogurt.