Starbucks workers at more than 100 U.S. stores will go on strike Thursday, petitioning stores during one of the company's busiest days.

The strike represents the largest labor action yet for the blitzing union, as more than 1,000 Starbucks workers across the country are expected to participate.

Starbucks Workers United, the union organizing the effort, seems to have chosen "Red Cup Day," one of the busiest of the year for the company, as the perfect time to demonstrate. The group is branding the protest as a "#redcuprebellion," taking to social media to promote its cause.

Starbucks Workers Union, the group organizing the strike, promotes its movement to its over 90,000 Twitter followers.

Red Cup Day is one of Starbucks' most profitable days, as customers are known to line up in front of stores in hopes of receiving a limited-edition reusable holiday cup. Customers need only order a holiday drink to be gifted the coveted drinkware.

Workers in over 20 states are expected to participate in the strike, says Starbucks Workers United, and workers are protesting unfair labor practices by the company.

Over 250 Starbucks stores have unionized, according to, with another 41 awaiting elections. Talks between the union and company have been fraught as both sides battle for their cause.

Starbucks claims a union is not necessary for workers, saying the company operates better when it has direct contact with workers. Workers say the company has not cooperated in negotiations and has acted in bad faith by firing employees who planned to join the union. In August, a federal judge ruled that Starbucks had to reinstate seven union organizers who were fired in Memphis, Tennessee.

In an April filing with the National Labor Relations Board, Starbucks Workers United claimed that interim CEO Howard Shultz was withholding benefits from workers who joined the union.

Customers swayed by the picketing workers don't need to worry about missing out on the limited-edition holiday cups. Some workers will be handing out similarly branded "union red cups" to customers supporting their cause.