of course you should drink water. Total abstinence won't benefit anything.
I usually drink water, herbal teas, and vege or vege/fruit juices.
First day is easy, second day is usually the challenge, after that it's all good.
You feel like you have more energy (when you probably don't). I did notice this time around at day 5 I was starting to struggle with my German and had to really concentrate to speak it properly. I broke the fast the day after.
Breaking a fast correctly is also important. You have to restart slowly. It was about 4 days before I ate any animal products again.