Dunkin’ Donuts is aiming to drive holiday sales and promote its Halloween-themed Boston Scream Donut and Halloween Pumpkin Donut with a cup-decorating challenge on Twitter and Instagram.

CHICAGO - SEPTEMBER 07: A cup of Dunkin' Donuts coffee and a donut bag sit on a counter September 7, 2006 in Chicago, Illinois. In an effort to compete with Starbucks in the lucrative coffee ...