Citing sustainability, Starbucks wants to overhaul its iconic cup. Will customers go along?

TEMPE, Ariz. (AP) — Bethany Patton steps up to the counter and places her pink mug into a shoebox-sized dishwasher. It spins. It whirs. Water splashes inside. After 90 seconds, the door opens and steam emerges. A barista grabs the mug, dries it and prepares Patton’s order — a 16-ounce Starbucks double espresso on ice.

For bringing her own cup, Patton gets $1 off her drink.

“Saving the environment is important and all, but I probably come here more in knowing that I’m going to get a dollar off,” says Patton, 27, a cancer researcher at…