It is Red Cup Day at coffee giant Starbucks, an unofficial holiday for java fans who enjoy discounts and rewards. Here's how it works: Stop by a participating Starbucks store on Thursday and get a free, 16-ounce holiday-themed reusable red cup when you purchase one of the coffee chain's special seasonal drinks.

Thursday is Red Cup Day at Starbucks, one of the most anticipated days of the year for Starbucks fanatics. The coffee chain rewards customers who order select holiday beverages with a free limited-edition red holiday cup.

"Red Cup Day," a favorite Starbucks holiday tradition that offers customers free reusable cups, takes place this week -- but there's a catch.