In a bowl, beat egg, milk and oil. Combine flour, sugar, baking powder and salt; stir into the egg mixture until smooth (batter will be thick). Peel, core and cut apples into 1/2-in. rings.
In an electric skillet or deep-fat fryer, heat oil to 375°. Dip apple rings into batter; fry, a few at a time, until golden brown. Drain on paper towels. Combine sugar and cinnamon; sprinkle over hot fritters. Serve warm.