Whenever I make a kong for the dogs at the shelter, I put small broken up treats in them and cover the holes with either easy cheese or peanut butter. It is a lifesaver for the poor shelter dogs who need things to stimulate their minds.

I make the kong the same way for my own dogs, but usually just give it to them if they're going in a crate. Since I don't crate them anymore, I seem to have lost my kongs