Payments at Starbucks Korea plunged over 10 billion won ($6.5 million) in the month of May, following a controversial promotion event criticized for evoking painful memories of the 1980 pro-democracy uprising, industry data showed Thursday.

The marketing fiasco has wiped out millions in sales, delivery worker unions have vowed to refuse orders, and government officials will ban the coffee giant from public events.…

Payments at Starbucks Korea plunged over 10 billion won ($6.5 million) in the month of May, following a controversial promotion event criticized fo...