Start by rinsing and draining the sauerkraut in a colander for about 5 minutes to reduce its saltiness.

Finely chop the red onion, bell peppers, and carrots. If using, cut the apples into bite-sized pieces.

In a large mixing bowl, combine the sauerkraut, chopped red onion, bell peppers, and carrots. Stir gently.

In a small bowl, whisk together olive oil, apple cider vinegar, salt, and pepper to taste.

Drizzle the dressing over the salad mixture and gently toss to coat.

Transfer the salad to an airtight container and refrigerate for at least 1 hour to meld flavors.

Before serving, give the salad a gentle stir and garnish if desired.