If you work in an office, chances are there’s a water cooler somewhere. And if there’s a water cooler, chances are there’s a stack of disposable paper cups (or possibly, even in this age, styrofoam). And chances are that most people will walk up, grab a paper cup, take it back to their desk and then throw it away.
Of course, all those paper cups end up in a landfill somewhere. And there’s the material to manufacture them (even if it’s recycled). And there’s the energy that went into manufacturing them.
So why not reuse that paper cup if you’re only using it for water? It’ll dry out between uses, so the water shouldn’t seep through the wax. If you have, say, one glass of water a day, and you use the same cup for a week, you’re cutting down your paper cup usage by 80%.
Or better yet: do you have a coffee mug? You need to wash it out anyway before you put more coffee in (unless you’re keeping it full all day long). Why not wash it out earlier, and use the mug when you want some water?
Sure, it’s less convenient than walking past the lunch room and grabbing a new paper cup. But let’s face it: you work in an office. And Americans, on the whole, don’t get enough exercise. You might as well take advantage of the extra activity for some incidental exercise.