01 - If using fresh pineapple, peel, core, and slice into 1/2-inch thick rings. Pat rings thoroughly dry with paper towels to remove excess moisture, which helps the batter adhere properly.
02 - In a medium bowl, whisk together flour, cornstarch, sugar, baking powder, and salt until well combined. Stir in cold sparkling water and egg (if using) until just combined. Do not overmix—small lumps are acceptable and will create a lighter, crispier coating.
03 - Pour vegetable oil into a deep skillet or saucepan to a depth of 2 inches. Heat to 350°F, maintaining temperature throughout frying. Use a kitchen thermometer for accuracy, as oil that's too cool will absorb excess grease while oil that's too hot will burn before the pineapple cooks through.
04 - Dip each pineapple ring into the batter, turning to coat completely. Allow excess batter to drip off for a few seconds before frying to prevent ragged edges and ensure even cooking.
05 - Carefully place battered rings in the hot oil, working in batches to avoid overcrowding. Fry for 1 to 2 minutes per side until golden brown and crispy. Remove with a slotted spoon and transfer to paper towels to drain excess oil.
06 - Dust warm fried pineapple rings generously with powdered sugar. Add a sprinkle of ground cinnamon if desired. Serve immediately while hot and crispy, accompanied by vanilla ice cream or caramel sauce for an indulgent dessert experience.