The holy month of Ramadan is started from today here in India. Ramadan Kareem to all my Muslim dp members and others too.
Why not drinking water during the day is healthy? Yoga recommends drinking hot water during fasting so the body can get rid of toxins. Keeping the poisons in the body all day is not healthy. God generally wants people to live healthy life styles. Also some spiritual people say food must be accepted during day time after sunrise up to sunset. Because after sunset the stomach needs to rest.
You might want to back those statements with some sort of authoritative reference, instead of simply making sweeping assertions without evidence whatsoever. Fasting is generally accepted as a healthy lifestyle, no one has ever shown any proof that not eating/drinking during the day will be harmful to your health.