Or at least simply having it with your in your travels throughout the day, so as to avoid the need to use a disposable cup for a drink.

Just yesterday, I had forgotten my water bottle in my bag while attending a meeting and ended up using a non-recycable cup for a few necessary sips of water.  Imagine how many times that happens across the country every day.  That brief moment to throw a cup into a landfill that will last there for a lifetime… what a good reminder to never forget it again!