Noni juice is best for humans who have knee or other joints pain.But I do not see any problem if you give a small dosage of noni juice to your dog.But be aware some dogs have allergic reactions to grape fruit which is a key ingredient in noni juice.
Noni juice is a good for the animals and you can use it. It is concentration of the special plants and it is extracted from plant. Many people use this for diet. For further details you can check this website for further details.