Beat sugar and eggs with a whisk until light and fluffy, about 5-8 minutes. Drizzle in oil. Add mashed bananas, pineapple, sour cream, and vanilla. Gently fold in the flour mixture and mix only to combine (do not overdo it). Pour into a lined loaf pan and bake for about 1 hour. Cool for 15 minutes in the pan and then turn out onto a wire rack and cool completely.