As donut lovers ring in National Donut Day this year on Friday, June 1, Dunkin’ Donuts is once again sweetening the celebration, heralding the holiday by offering guests a free classic donut of their choice (while supplies last) with the purchase of any beverage. The offer is good all day on June 1 in store and through On-the-Go Mobile Ordering at participating Dunkin’ Donuts restaurants nationwide.