Boil the potatoes, beets, and carrots separately in salted water until fork tender. The potatoes and beets will cook for about 35-45 minutes and the carrots will cook in about 15 minutes. When cool enough to handle, peel the beets, and dice the vegetables into ¼ inch pieces.

Place the potatoes, beets, carrots, cucumbers, apple, and sauerkraut into a large mixing bowl. 

Add the sunflower oil, apple cider vinegar, salt, and sugar in a small bowl. Whisk until well combined.

Pour the dressing over the vegetables and gently stir the salad until evenly coated.

Serve at room temperature.