Drinking can be a displacement behavior and if the opportunity is there some dogs will drink excessively if stressed or anxious. It can also become a learned behavior--they have self-soothed by drinking so often that it becomes almost a habit to look for something to drink when feeling stressed or anxious. Excessive drinking can be a true compulsive behavior as can compulsive licking.
On the other hand, excessive drinking and frequent/uncontrolled urination are both symptoms of some rather serious medical issues. I would be concerned if a dog in my care were doing both. Does her owner have a dog door at his home. If so, it's possible that he isn't even aware of the frequency of his dog's nighttime urination.
You said the dog is "brain-damaged". Do you know this for a fact, or are you saying that because of the spinning behavior? Spinning can be an OCD behavior in dogs and if this is the case it's likely that it can be effectively treated with medication and some relatively simple behavior management. Spinning can also be caused by high arousal/stress and anxiety. Given the dog spins and perhaps comupulsively drinks, I'm thinking anxiety disorder, OCD, or neurological issues aren't out of the question.