Have you heard of the concept of tap water and a nice glass or metal water bottle that's added microplastic free?
You're assuming the presence of freely accessible water fountains and/or otherwise hygienic means of refilling a water bottle.
That tends to be a lot less common here, unless you specifically go out of your way to visit college campuses or something similar.
(Before the pandemic the situation was slowly improving, but I'm not sure if that has continued.)
Or are you just suggesting someone carries a few liters of water from home to start with?