Forcing a child when they have a choice as he is 10 years old is abuse and that is how I parent , I agree on the brushing of the teeth 100% as that is for there benefit of personal care but I wouldn't force the 10 year old to do it as I have sat down with him and explained that that is there for personal health and he brushes his teeth atleast twice a day .
Forcing a child to drink something via withholding everything else to the point of dehydration is therefore force when they should have a choice . I wouldn't do this to an adult so I wouldn't do it to my child .
And if your child was equally picky with food?