In a large bowl, combine the flour, sugar, baking powder and salt. In another bowl, whisk eggs and milk. Stir in pineapple. Stir into dry ingredients just until blended.
In an electric skillet or deep-fat fryer, heat oil to 375°. Drop batter by heaping teaspoonfuls a few at a time, into hot oil. Fry until golden brown, about 1-1/2 minutes on each side. Drain on paper towels. Dust with confectioners' sugar.
Editor's Note: Doughnuts may be frozen in an airtight container for up to 1 month. To reheat, place on a microwave-safe plate and microwave on high for 5-10 seconds or until warm. Dust with confectioners' sugar.