One of the major things we have control of is our water supply. For years my boss has bought us bottled water so that people will drink water on hot days and stay hydrated. I have been complaining to him for years about how unsustainable it is, how expensive it is, and all the unnecessary waste we are creating.
I think he finally got tired of listening to me, because when he finally said "fine, what else can we do" I quickly told him we could get a large pitcher that filters the tap water. He asked some people on staff and they agreed with me that they would drink the water that way. Two days later I came in to work and we had a large, beautiful filtered water dispenser in our office.
Image courtesy of Filters Fast
Although people still buy bottled water and bring it to work (even though I tell them every time about the environmental impacts and financial impacts), at least they are refilling those bottles with water instead of throwing it out and getting a new one every time they empty it. And for the people who do bring their own bottles, we can enjoy tasty water as much as we like. (and for my one coworker who always forgets his bottle, he just waterfalls from the cooler... its a sight to see.)