We have one girl that gobbles down water all day and the other hardly ever picks up a drink. I use a couple of tricks to help her stay hydrated.
She loves cucumber and cucumber is over 90% water, watermelon and strawberries work well too. Did you know you can get a real straw - straw - actually made out of real straw. They are all natural, organic and everything tastes better sipped through a straw. Also she simply seems to forget, so I always make it easily available... or ask her to hold my drink for me, she usually goes for it then!