I give my chin extra twigs, a single rose hip, or a pinch of rolled oats once or twice a week. I also give half a dandelion, alfalfa hay cube, or a "cookie" every few weeks as a special treat. I made the "cookie" mostly out of food and hay, with some treats mixed inside. She doesn't really care for them though.
I also use her dust bath as a treat/reward. Instead of giving it to her, I go through out little "treat" routine but instead of a rose hip, she gets her dust.