01 - If using fresh pineapple, peel, core, and slice crosswise into ½-inch thick rings. Pat thoroughly dry with paper towels to remove excess moisture for better batter adhesion.
02 - In a medium mixing bowl, whisk together flour, cornstarch, sugar, baking powder, and salt until well combined. Gradually stir in cold sparkling water and egg (if using) until just combined—do not overmix as this affects texture. The batter should be light and slightly lumpy.
03 - Pour vegetable oil into a deep skillet or heavy saucepan to a depth of 2 inches. Heat over medium-high heat until oil reaches 350°F on a deep-fry thermometer. Maintain this temperature throughout frying for optimal results.
04 - Dip each pineapple ring into the batter, turning to coat completely. Allow excess batter to drip off briefly before frying to prevent clumping and ensure even cooking.
05 - Carefully lower battered rings into hot oil, working in batches to avoid overcrowding. Fry for 1 to 2 minutes per side until golden brown and crispy. Using a slotted spoon, transfer to paper towels to drain excess oil.
06 - Dust generously with powdered sugar while still warm. Add a light sprinkle of cinnamon if desired. Serve immediately for best texture, accompanied by vanilla ice cream or warm caramel sauce for an elevated presentation.