Orange Scones with Orange Glaze
1 medium egg 1 tablespoon milk, or as needed 1 tablespoon orange zest 1 ½ tablespoons white vinegar 1 ⅓ cups all-purpose flour 2 tablespoons confectioners' sugar 2 tablespoons white sugar, divided 2 ½ tablespoons orange zest 4 teaspoons orange juice 6 tablespoons orange juice cooking spray ¼ teaspoon baking powder ¼ teaspoon salt ½ cup confectioners' sugar ½ stick cold unsalted butter, cubed ½ teaspoon baking soda