My child chews on her sleeves, how do I get the stains out?

My 6 year old has a habit of chewing on different things. It started with chewing on her hair, which made it smell horrible and unable to comb. We broke that habit, now that it's getting cold outside shes chewing on the sleeve of her shirt. We like to buy her nice clothes, but she wears a shirt once and its stained with food, spit and dirt from getting drooled on and going outside for recess. Any suggestions on how to break the habit and/or get her sleeves cleaned? I've been spraying them with stain removal and letting them sit over night and it's not working.