To prepare pineapple, cut off both ends. Remove rind and eyes with sharp knife. Cut pineapple into lengthwise quarters. Remove core; cut fruit into chunks. Measure 1 cup pineapple; refrigerate remaining pineapple for another use. Place 1 cup pineapple and strawberries in a large bowl; sprinkle with sugar. Let stand until ready to use. Divide fruit among four large glasses; add 1/2 cup sherbet to each glass. Pour 1 cup lemon-lime beverage into each glass. Serve immediately.