Water

Why this is important:

"Despite its association with purity and cleanliness, bottled water is bad for the environment. It is shipped at vast expense from one part of the world to another, is then kept refrigerated before sale, and causes huge numbers of plastic bottles to go into landfills.”
-
Bad to the Last Drop, New York Times

Drinking bottled water takes the water out of the watershed area, which can prevent the source from being replenished.

Not to mention, that “tap water is more stringently monitored and tightly regulated than bottled water." Bad to the Last Drop, New York Times

What you can do:

Buy a reusable water bottle, and use it! If you are worried about water quality, there are many filter systems available.