Combine cake mix with eggs, oil, buttermilk and sour cream. Beat with a mixer on medium speed until combined.
Next add orange juice, rum, coconut extract and diced pineapple. Beat into cake on a low speed until combined.
Fill cupcake liners 2/3 full and bake for 12-15 minutes. Check after 12 minutes, and bake another 2-3 minutes until tops are golden or until you can insert a toothpick and it comes out clean. Baking times will vary by oven.
Allow cupcakes to cool in the pan for 5 minutes and then transfer them to a wire rack to cool.