Place 2 to 3 inches of oil in a deep cast iron skillet and heat to 350-375 degrees Fahrenheit.
Line a platter with paper towels to drain excess oil after frying.
Core the apples and slice them into 1/2-inch thick rings.
Pat the apple rings very dry with paper towels to ensure the batter adheres.
In a large bowl, whisk together the flour, 3 tablespoons sugar, 1/2 teaspoon cinnamon, baking powder, and salt.
In a separate bowl, combine the milk, egg, 1 tablespoon oil, and maple syrup.
Whisk the wet ingredients into the dry ingredients until a smooth batter forms.
Dip each apple ring into the batter, ensuring it is fully coated, then let the excess drip off.
Carefully drop the coated rings into the hot oil, frying for 3-4 minutes per side until golden brown.
Remove the fritters and place them on the paper-towel-lined platter.
Immediately toss the warm fritters in a mixture of 1/4 cup sugar and 1 teaspoon cinnamon.