Customers who return to Starbucks with the custom cup, or any reusable cup, will receive a 10-cent discount on their order and Starbucks Rewards members can earn 25 stars when they bring back their reusable red cup for future orders.

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.