I also keep water in my car. I work at home in two areas of my house, so I have two pretty drink cups that I keep filled in both places all day.
I add a little dash of lemon or lime to it once a day for a little shakeup.
I also have set times that I drink a full drink cup full (maybe it's about 2-3 cups) and that's as soon as I get up in the morning, before my lunch, and with my vitamins at bedtime. This does have me up during the night, but it doesn't bother me. I have a cup on my nightstand as well and sip during the night.