Drink water! Just drink water. Water is water. Any water is still better than other beverages.
Every organ in our bodies require water. Even for good elimination we need water.
A good rule is one half your body weight in ounces daily. That's a lot of water! Especially since we drink caffeinated beverages like coffee, tea, pop, energy drinks, etc., that actually dehydrate the body. Remember to drink an additional amount of water (equal to the caffeinated beverage intake) to account for the caffeine effect.
Filtered? Bottled? Tap? There is a lot of information about what water to drink. So let's break it down.
Try to drink water in glass bottles, or in BPA free plastic bottles. Purify water by reverse osmosis, ultraviolet, filter, tabletop gravity, etc. Spring water is also recommended, but steam distilled is considered a 100% pure process.
And don't forget that swimming, taking baths and hot tubs actually dehydrate you, so be sure to drink extra water.