I added raisins to mine, which is optional, and there's room in the recipe to add very well drained crushed pineapple if you enjoy that flavor in your carrot cake. (paleorunningmomma.com)
orange rind, grated 3 cups very fine carrots, and 1 cup processed sweet coconut, and I added one 8 ounce can of drained crushed pineapple instead of the 20 ounce can. (kingarthurflour.com)
Personally, I stir loosely drained crushed pineapple into the batch just as it's done. (smittenkitchen.com)