We don't tell you how much water to drink in the plans, but here's a good guideline:
"The Institute of Medicine determined that an adequate intake (AI) for men is roughly 3 liters (about 13 cups) of total beverages a day. The AI for women is 2.2 liters (about 9 cups) of total beverages a day."
That's a pretty decent amount of water, so you'll probably want to be drinking constantly throughout the day. If you do it in just 5 sittings (maybe 3 meals and 2 snacks), a male should drink about 2.5 cups of water each sitting, and a female, about 2 cups each sitting.
Personally, I just keep one of these next to me all day: a thermos hydration water bottle and then take gulps from it whenever I feel like it. It's probably the best water bottle I've ever used (I tried maybe 8 of them before I stuck with this one), and it has a nifty counter on it so you can keep track of how many times you've refilled it and make sure you're meeting your goal.