No more to-go cups? Starbucks to discontinue disposables by 2030.

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 Ms. Patton’s order – a 16-ounce Starbucks double espresso on ice.

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

“Saving the environment is important and all, but I probably come here more knowing that I’m going to get a dollar off,” says Ms. Patton, a researcher at Arizona State University. Two friends who came on the afternoon coffee run nod as they hold the cups that they, too, brought along.