Preheat the oven to 350 degrees F (175 degrees C). Grease or line 16 cupcake cups with paper liners.

Cream sugar and butter for cupcakes together in a medium bowl. Beat in eggs, one at a time. Stir in vanilla extract and coconut extract. Add flour and baking soda and mix well. Stir in milk and pineapple juice until batter is smooth. Fold in crushed pineapple. Spoon batter evenly into the prepared pan.

Bake in the preheated oven until tops spring back when lightly pressed, about 25 minutes. Let cool completely.

While cupcakes cool, cream butter and vanilla extract for frosting together in a large bowl. Blend in confectioners' sugar, 1 cup at a time, beating well after each addition; you may need to add an additional 1/4 to 1/2 cup based on your liking. Beat in milk and pineapple juice until light and fluffy. Frost cooled cupcakes or store in the refrigerator until ready to use.