sisters toddler is becoming a biter, what do we do!?

Help me help my sister, my sisters LO is hell on wheels and will be turning two this november. Recently at the daycare me and her both work at she got her room moved up and ever since the day she moved up rooms she’s been biting her friends 🙄 my sister has tried everything.. she has tried teething rings, teething medicine, not rewarding her with good things (my niece is spoiled and anytime she cries she gets what she’s wanting) popped her hand, popped her butt, and even bit her back. Any recommendations are welcome.