Preheat oven to 375˚F.
In a large bowl, combine sugar, flour, and reserved 6 tablespoons pineapple juice.
Add pineapple chunks and pineapple tidbits (or crushed pineapple), and toss well to combine.
Combine crushed Ritz crackers and melted butter.
Spread Ritz cracker topping evenly on top of pineapple mixture.