Tim Hortons Cafe & Bake Shop is paying it forward in celebration of National Random Acts of Kindness Week by picking up the bill for unknowing guests at the drive-thru.

This is the third year Tim Hortons Cafe & Bake Shop has held its Random Cups of Kindness event. In 2012, the restaurant chain treated approximately 5,500 guests to a free order. This year, it plans on treating even more customers in approximately 300 restaurants.

Doing good at the drive-thru isn't a new concept to the bakery cafe chain. Restaurant owners, managers and team members regularly witness customers paying for a stranger's order—especially during the morning rush when drive-thru lines can get particularly long.

"Our guests' generosity to one another continues to amaze and inspire us," says Mike Meilleur, executive vice president, Tim Hortons US. "What started out as just a few instances of guests paying it forward here and there has now become a bit of a fun Tim Hortons tradition."

A customer who receives their order for free will be given a coffee card good for one, free medium size coffee to pass along to someone else to continue spreading kindness.

Tim Hortons Cafe & Bake Shop's Random Cups of Kindness event kicks off in all US markets at select restaurants on Monday, Feb. 11. The program ends Sunday, Feb. 17.

National Random Acts of Kindness Week is celebrated Feb. 11-17 and was founded by the Random Acts of Kindness Foundation.