Combine water and sugar in a large pot; bring to a boil. Cook and stir until the sugar dissolves, about 3 minutes. Cool in the refrigerator.
Put 1 banana and about 1 cup pineapple juice in a blender; blend until smooth. Repeat until all bananas are pureed into pineapple juice; stir into the pot with the simple syrup. Add orange juice concentrate and lemonade concentrate to the pot; stir. Divide the mixture into smaller containers and freeze until mostly solid.
Put frozen mixture into a large punch bowl. Thaw until slushy, but stirrable. Stir lemon-lime carbonated beverage into the punch bowl. Garnish with orange slices.