Sift together the flour, baking soda, cinnamon and salt. Stir together and set aside.
In a separate bowl stir the sugar, sour cream, egg and butter until it is smooth. Then stir in the flour mixture until a dough forms.
Cover the bowl and chill the dough for at least 30 minutes.
Roll the dough out until it is 1/2 inch thick. Then cut it into small rounds with a biscuit or donut cutter.
Heat vegetable oil to 350 degrees. Cook the dough for 1-2 minutes.
Remove from the oil and coat donuts in the granulated sugar and cinnamon.