National Mustard Day is this weekend â itâs the first Saturday in August â and this year? Frenchâs has teamed up with Dough Doughnuts to create the new limited-edition Frenchâs Mustard Donuts. Itâs described as âa classic glazed doughnut with a vibrant sweet and savory yellow mustard coating, topped with a yellow mustard cake crumble.â If that sounds tasty to you and youâre in New York â or plan to be there this weekend â you can score one for free at one of the Dough Doughnuts locations on Saturday.