I don't know much about this kinda stuff but I just wanted to comment on the type of disposable cup you get. I, personally, try to avoid Styrofoam whenever possible for environmental reasons. If your area has a lot of eco-friendly people its something to consider. I know there are some eco-friendly options out there.
And by the way, ceramic mugs and cups are the most eco-friendly - they're reusable!
might depend on the cost of water, heat, and soap, plus keeping the area clean and dealing with health inspections. With paper cups, all you have to do is make sure that there is a trash bin.
That said, as a customer, for long sits, I'd rather have a mug. it's lest wasteful, doesn't make one feel rushed.
Also, paper over styrofoam, always. Styrofoam is very hard to recycle from what I hear, and takes forever to break down. Paper can be recycled, they sell recycled paper cups and sleeves, and also breaks down quicker.
We use 100% biodegradable paper cups. No "plastic" lining inside, so they breakdown in 8 weeks. I buy them from Clovernook Industries in Ohio. Super folks that hire the visually impaired. Makes me feel good about what I do.