Sassy Juice! My hairstylist told me about this and when I was telling some friends at scrap booking, three other people had not only heard about it, but use it! I am a HUGE believer in it.
Sassy Juice is simply white vinegar. Completely harmless, but bitter tasting, white vinegar. I was told to put some in a little spray bottle and when we had an issue that involved the mouth (biting, sticking out tongue, bad language, sassy talk, etc...) then spray the vinegar in the mouth. Now, good luck getting anybody to open their mouth! So, all I do, is stick my finger in the vinegar and put it in their mouth. You can simply touch their lips or get it in as far as their gums but I will tell you it is TOTALLY effective!
My hairstylist was telling me how her 4 year old son was using the F word after hearing dad yell it at the TV sports game. She could not get him to stop saying it. Somebody told her about Sassy Juice, she used it once, and he has NEVER said it again.
My 4 year old son lied about something and we explained the issues with lying, trust, etc. and told him if he ever did it again that we would put something yucky in his mouth for saying yucky things (lying). Let me tell you, we did the vinegar just once and he has never lied again.
My 3 year old daughter started sticking her tongue out at people. We did the warning, explained why this was not appropriate and that she would get something yucky in her mouth if she ever stuck her tongue out at somebody again. She did it a few days later, she got the vinegar rubbed on her gums, and she has NEVER done it again.
I am a huge believer in it!! I can not believe how well it works. It is perfectly harmless. It simply tastes bad. Just one finger dipped in the vinegar and put in their mouth and you have just solved your problem! I suggest not over using it so they get used to the flavor. I have only used it for verbal or mouth related issues. And only used it once!
It is the perfect solution for biting because it is mouth related. :)
Good luck!