Preheat the oven to 350°F and pray a 2-quart baking dish with nonstick cooking spray. Drain the pineapple very well and reserve 6 tablespoons of the juice for the recipe.
In a large bowl, stir together the sugar, flour and 6 tablespoons of the juice. Add the pineapple and mix well. Pour it into the prepared dish. Sprinkle the cheese over the top.
In a medium bowl, add the melted butter to the crushed cracker crumbs and stir to coat them in the butter. Sprinkle them evenly over the cheese. Bake for about 30 minutes and then allow the casserole to rest for about 10 minutes and thicken before serving.