In a large mixing bowl, combine finely chopped corned beef, shredded Swiss cheese, well-drained sauerkraut, cream cheese, Dijon mustard, garlic powder, onion powder, and black pepper. Mix these ingredients thoroughly until everything is evenly incorporated.

Cover the mixing bowl with plastic wrap and refrigerate the filling for at least 30 minutes.

Using a tablespoon or small cookie scoop, take the chilled mixture and form it into 1 to 1.5-inch balls. Place each ball onto a parchment-lined tray.

Prepare your breading station with one bowl of flour, another with beaten eggs, and the third with panko breadcrumbs.

Heat vegetable oil in a deep pot or large skillet over medium heat until it reaches 350°F (175°C).

Carefully add the breaded Reuben Balls to the hot oil in batches, frying for about 2–3 minutes until golden brown and crispy.

While the Reuben Balls are frying, whisk together mayonnaise, ketchup, sweet relish, hot sauce, and paprika in a mixing bowl until smooth.