Preheat the oven to 350 degrees F.
In a large bowl, stir together the sugar and flour. Gradually stir in the cheese. Add the drained pineapple chunks, and stir until ingredients are well combined. Pour the mixture into the prepared casserole dish.
In another medium bowl, combine the cracker crumbs, melted butter, and reserved pineapple juice, stirring with a rubber spatula until evenly blended. Spread crumb mixture on top of pineapple mixture. Bake for 25 to 30 minutes, or until golden brown.