Thousands of Starbucks union members walked off the job on the coffee retailer's biggest promotional day of the year. Timing is everything.

Starbucks's "Red Cup Day" is one of the biggest revenue-and-PR days for the global coffee retailer. Each year, its iconic white cups get their festive makeover, and Starbucks offers customers a free, reusable red cup with certain purchases of holiday drinks. Coffee lovers – especially fans of flavours such as gingerbread, pumpkin spice and apple crisp – turn up in droves, often posting their beverages on social media.

But this year, on 16 Nov, many regular staffers at more than 200 US stores weren't there to pour peppermint hot chocolate into red holiday vessels. Some locations weren't open at all during this "Red Cup Rebellion".

Thousands of Starbucks Workers United (SBWU) union members in US locations in states including New York, Texas, Massachusetts, Washington and Illinois went on strike on the high-profile day to fight for better workplace conditions regarding staffing, scheduling and contract negotiations.