01 - If using fresh pineapple, peel, core, and slice into 1/2-inch thick rings. Pat rings completely dry with paper towels to ensure batter adheres properly. If using canned rings, drain thoroughly and pat dry.
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. The batter should be thin and slightly lumpy.
03 - Pour vegetable oil into a deep skillet or saucepan to a depth of 2 inches. Heat oil to 350°F, maintaining temperature throughout frying. Use a kitchen thermometer for accuracy.
04 - Dip each pineapple ring into the batter, allowing excess to drip off. Ensure each ring is evenly coated but not heavily burdened with batter.
05 - Carefully place battered rings into hot oil, working in batches to avoid overcrowding. Fry 1–2 minutes per side until golden brown and crispy. Remove with a slotted spoon and drain on paper towels.
06 - Dust warm fried pineapple rings generously with powdered sugar. Sprinkle with ground cinnamon if desired. Serve immediately while warm and crispy, optionally accompanied by vanilla ice cream or caramel sauce for dipping.