In a large bowl, combine the potatoes, apples, sauerkraut and eggs. Combine the flour, salt and pepper; stir into potato mixture.
Heat 2 tablespoons oil in a large nonstick skillet over medium heat. Drop batter by 1/4 cupfuls into oil; press lightly to flatten. Fry in batches until golden brown on both sides, using remaining oil as needed. Drain on paper towels. Top with sour cream and green onions if desired.