Preheat the oven to 425 degrees F (220 degrees C). Line a baking sheet with aluminum foil and grease with cooking spray.
Mix flour, 1 tablespoon sugar, baking soda, baking powder, and salt. Cut in butter using a pastry cutter. Mix in orange zest.
Make a well in the center of the flour mixture. Whisk orange juice, egg, and vinegar together and pour into the flour mixture. Stir until moistened and sticky.
Transfer dough to a floured surface and knead gently about 10 times. Pat into a 6x8-inch rectangle. Cut rectangle into 4 squares; cut each square diagonally into 8 triangles. Arrange scones on the prepared baking sheet. Brush tops with milk and sprinkle with remaining 1 tablespoon sugar.
Bake in the preheated oven until golden brown, about 10 minutes.
Make the orange glaze while the scones are baking. Mix 1/2 cup plus 2 tablespoons confectioners' sugar and orange juice until thick and smooth; glaze should drip slowly off the back of a spoon. Mix in orange zest.
Dunk warm scones in the glaze to fully coat the tops. Let stand for 5 minutes before serving.