Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9x5 inch loaf pan and line with wax paper.
In a large bowl, combine sugar, eggs, vegetable oil, pineapple juice and pineapple; mix well. In a separate bowl, sift together baking powder and flour. Stir flour mixture into pineapple mixture. Fold in macadamia nuts. Pour batter into prepared pan.
Bake in preheated oven for 50 to 60 minutes, or until a toothpick inserted into center of loaf comes out clean.