M.C.
Hi W.,
I have a two year old. She try's to do this with me but I just do not allow it. She will ask for milk to drink and like you said in the next second ask for water. I simply look at her tell her she can have her milk or nothing at all. 90% of the time this works. She takes it and goes about her business. I also allow her each day to put her cups in yhe fridge. She has 3 in there one with milk, one with juice, one with water or kool-aide. This way when she gets thirsty she can go pick it out herself. Hope this helps