If you like free doughnuts, Friday was your lucky day because this is National Doughnut Day. To celebrate the occasion, Dunkin Donuts says it will give a free doughnut to anyone who buys a beverage while supplies last and Krispy Kreme says it's giving away a free doughnut with no purchase necessary at participating locations. National Doughnut Day got its start back in 1938 when the Salvation Army used doughnuts to raise money during the Great Depression.