01 - If using fresh pineapple, peel, core, and slice crosswise into ½-inch thick rings. Pat each slice thoroughly dry with paper towels to remove excess moisture, which prevents proper batter adhesion.
02 - In a medium mixing bowl, whisk together the flour, cornstarch, sugar, baking powder, and salt until evenly blended. Pour in the cold sparkling water and add the egg if using. Stir gently with a whisk just until combined—small lumps are acceptable. Avoid overmixing, which develops gluten and makes the batter tough.
03 - Pour vegetable oil into a deep skillet or heavy saucepan to a depth of 2 inches. Heat over medium-high heat until the temperature reaches 350°F. Use a kitchen thermometer to verify accuracy, or test by dropping a small amount of batter into the oil—it should sizzle immediately and rise to the surface.
04 - Working with one piece at a time, dip a pineapple ring into the batter, turning to coat completely. Lift and let excess batter drip off for 2-3 seconds. The coating should be thin and even—thick batter creates a doughy texture.
05 - Carefully lower 2-3 battered rings into the hot oil, taking care not to overcrowd the pan. Fry for 1-2 minutes on the first side until deep golden brown, then flip and fry an additional 1-2 minutes. Transfer finished rings to a wire rack or paper towel-lined plate to drain.
06 - While still warm, generously dust the fried pineapple rings with powdered sugar. For enhanced flavor, add a light sprinkle of ground cinnamon. Serve immediately while the exterior remains crisp, accompanied by vanilla ice cream or warm caramel sauce if desired.