In a large bowl, add flour, sugar, baking powder and salt. Mix with a fork. Add in juice, eggs, extract and oil. Stir well with a fork until it's a smooth batter. A few little lumps are fine, but it should be mostly smooth.
Heat the donut machine, grease it and fill the donut cavity with batter. You want to go almost all the way to the top. Close and let bake for 3-5 minutes or until golden brown.