I explained that I saw a documentary ~10 years ago where the claim was if you can do one thing for the environment, please stop purchasing bottled water. It seemed like an easy request, so why not.
I then rhetorically asked him if he "felt good" about himself because he doesn't just throw his trash out the car window, which is what we city kids (and adults) used to do in the early 80s. "No you don't do it and you don't think about it, right ? It's the same with my water bottle. I don't lecture anyone, and I honestly didn't think once about what he or others are doing."
Culture changes many times for the better. It's odd though how some people are the last to get the memo despite similar demographics.