Preheat your oven to the temperature specified on the cake mix box. Grease a 9×13 inch baking pan.
Prepare the cake mix according to the package instructions. Pour the batter into the prepared baking pan.
Bake according to the package instructions, or until a toothpick inserted into the center of the cake comes out clean.
Cool the cake slightly on a wire rack for about 10 minutes.
Making the Pineapple Filling:
While the cake is baking, combine the crushed pineapple (with its juice) and sugar in a medium saucepan. Cook over medium heat until the sugar dissolves and the mixture is slightly thickened, about 5 minutes. Remove from heat.
Poke holes all over the warm cake using the handle of a wooden spoon or a similar utensil.
Pour the warm pineapple mixture over the cake, making sure it seeps into the holes.