I got this idea from Williams-Sonoma. All you have to do is slice the apple*, cut out the core with a small round cookie cutter, knife or corer, and fill with:
◦ Peanut or sunflower butter
◦ Raisins
◦ Raw rolled oats (optional)
*Can also squirt apple with a little lemon juice so it doesn’t turn brown
~The Pet Depot