I stuff Zulu's Kong with no salt added canned green beans. The have almost no calories, and you can cram the Kong full of them. Easy to clean too. I make my own peanut butter, unsalted roasted peanuts in the food processor until smooth. After it sits a while the oil will rise to the top and can pour out a little at a time. I use just enough PB to seal the top and put them in the freezer. Zulu runs to his crate the second I open the freezer. He loves it!