Cook pasta as directed on package. Strain, and place in a large stainless steel bowl. Add apple cider vinegar, carrots, and onions, and stir to combine. Refrigerate for 20-30 minutes or until pasta is slightly cooled.

Meanwhile, in a small mixing bowl, whisk together mayo, milk, sugar, salt, and pepper until completely combined.

Once pasta has cooled, remove from the refrigerator and stir in dressing until completely coated. Enjoy immediately or store in an airtight container in the refrigerator for up to 2 days.