It's really tough but I think I'd just got to the point where I would have tried anything tbh I felt desperate. I had a child that terrorised the whole family that could cope just fine on 20 minutes sleep in 24 hours and was completely feral. Nothing I had tried worked, he didn't understand rules or incentives, he didn't care enough about anything for it's removal to have any effect nor did he want anything desperately enough either. Initially I fed him wotsits as rewards, one wotsit for every positive,he probably ate bags and bags of wotsits for weeks on end, then he had biscuits lots and lots of biscuits and I figured I deal with any teeth issues later. In time it was stickers and then yu gi oh cards and then coins and later still a thumbs up. If you would have told me that in time he'd behave for nothing more than a thumbs up gesture I would have laughed and cried but it's true at one point the only reward he needed was a thumbs up.