I have put yogurt, peanut butter, and cheese whiz in my babies' kong. I have frozen the yogurt and peanut butter as well. For the yogurt I just used whatever I had in my freeze (generic low fat) and for peanut butter (low fat jif). Cheese whiz is probably their FAVORITE and I just use generic for that as well (I'm a generic queen!)
They don't get these EVERY day but on most days.
Enjoy!