Water also helps detoxify the body meaning better liver function - your body will absorb more nutrients from the food you eat.
Putting any sort of flavouring or sugar in the water is more or less 'polluting' it.
more health benefits of drinking water:
regulate appetite
increase metabolism
boost energy levels
less water retention
alleviate some headaches
help reduce blood pressure
help reduce high cholesterol
ease joint pain
decrease in risk of some cancers
less chance developing kidney stones
release toxic waste products
improves skin
I found that and more
here!