In a small mixing bowl, combine granulated sugar and ground cinnamon. Set aside.
In a medium-sized bowl, combine the all-purpose flour, milk, eggs, and granulated sugar. Stir until the mixture is smooth and free of lumps. Set the batter aside while you prep the apples.
Peel the apples. Then, use an apple corer or a knife to remove the cores. Then, cut the apple into thin rings. The rings should be about ¼-inch thick. Each apple should give you 4 to 5 rings, depending on how thick you slice them.
Pour the vegetable oil into a deep skillet or frying pan, making sure you have about an inch of oil in the pan. Heat the oil over medium-high heat until it reaches 350°F. Using a digital thermometer is a good idea to monitor the oil temperature and ensure it’s hot enough for frying.
Dip each slice of apple into the batter, letting any excess batter drip off before placing the ring into the hot oil. Fry the apple rings in small batches for 3-4 minutes on each side or until they are golden brown. Use a slotted spoon to remove the apple rings from the oil and place them on a plate lined with paper towels to absorb any excess oil.
While still hot, dip each apple ring into the cinnamon sugar mixture, ensuring they’re fully coated.