My daughter drinks alot of water, but there's a period (a week or two) she doesn't drink water also, all she wants are juices, milk, chocolate milk etc.... At that time i found out I have her too much other drinks instead of water so I just stopped giving her anything else either than water and milk. i stayed very firm that there's nothing but water for her. At first she doesn't drink but when she is really really thirsty, she begged me for water. So I guess in your case, you have to let your son knows you are the one in charge here, tell him it's either water or nothing. It will take some time but it will definitely work. Right now she will drink whatever I give her.
For brushing teeth, my daughter was like your son also when she was smaller. But I bought some very cute and colorful toothbrushes, then I brush my teeth in front of her everyday. Also I'll help her brush her teeth first and then give her a little mirror to look into and let her brush it herself. Meanwhile, you have to say"wow, you are really a big boy now, look what a good job you have done" something like that. Right now my daughter loves to brush her teeth
Thank you for all your advices! I will keep teaching him to brush the teeth, try make it an interesting activity to him and avoid make him dislike this activity.
Thanks again!!!