Starbucks workers at more than 100 U.S. stores walked out on strike Thursday. It’s largest labor action since a campaign to unionize Starbucks’ stores began late last year. The walkouts coincide with Starbucks’ annual Red Cup Day, when the company gives free reusable cups to customers who order a holiday drink. Workers say it’s often one of the busiest days of the year. They say they are seeking better pay, more consistent schedules and better staffing. Starbucks opposes the unionization effort. The Seattle coffee giant has more than 9,000 company-owned stores in the U.S.