Begin by boiling a large pot of salted water. Add the macaroni pasta and cook according to package instructions, about 8-10 minutes until al dente. Drain and return to the pot.

While the pasta is still warm, pour the apple cider vinegar over it, tossing gently to coat. Allow it to cool for about 10 minutes.

In a large mixing bowl, whisk together the mayonnaise, whole milk, and brown sugar until smooth. Add salt and pepper to taste.

Once the macaroni has cooled, add it to the bowl with the dressing and stir well to coat evenly.

Gently fold in the chopped celery, grated carrot, and chopped onion to retain their crunch.

Cover the bowl tightly with plastic wrap or transfer to an airtight container. Refrigerate for at least 2 hours.

Before serving, give the salad a gentle stir. Adjust seasoning if needed and serve chilled.