In a blender, combine water, lemonade concentrate, strawberries, and ice. Blend until fully incorporated. Pour mixture into a freezer container and freeze for at least 12 hours. (It can be stored in the freezer up to 3 months.)

When ready to serve, remove from freezer and let stand at room temperature about 1 hour before serving. Divide frozen slush into 4 large glasses and pour 1/4 cup lemon-lime soda in each cup. Serve immediately. Makes 4 servings, but can easily be doubled.