Well, Yet again, Kinda sounds weird, But Squeeze Lime juice in a spray bottle, And Open his mouth and Spray it if he chews or bites something, Dont spray it on the thing hes chewing on, That would just make a mess, Spray it in his mouth.

By the way, Dont put it in like a windex bottle or something, If you can buy an empty spray bottle at the store and Wash it out very good, Squeeze lime juice into it.