The Workers United union targeted Starbucks’ Red Cup Day to stage a one-day walkout at more than 200 of the coffee retailers locations across the U.S. in an action organizers said was the biggest strike yet in an ongoing unionizing effort. The union scheduled the event to coincide with one of the busiest days of the year for Seattle-based Starbucks’ outlets where customers can get a free reusable cup with the purchase of a specialty holiday beverage. Workers United expected 5,000 workers to participate in a day that included picketing and visits with employees at non-union stores.