Peel and cube small potatoes into bite-sized pieces. In a large pot, bring salted water to a boil over medium-high heat. Carefully add the potato cubes and boil for 5 minutes until just tender.

Stir in the elbow macaroni and continue boiling for an additional 6-8 minutes until both the macaroni and potatoes are soft yet firm to the bite.

Once cooked, drain the potatoes and macaroni thoroughly in a colander. While still warm, toss them with apple cider vinegar to enhance flavor absorption; allow the mixture to cool for about 10-15 minutes.

In a large mixing bowl, combine mayonnaise, milk, granulated sugar, and a pinch of salt and pepper. Mix until smooth and creamy.

Once the potato and macaroni mixture has cooled, gently fold it into the dressing. Add grated carrot, finely grated onion, and chopped hard-boiled eggs, stirring until well combined.

Transfer the combined salad into an airtight container or bowl and cover it tightly. Refrigerate for at least 4 hours, or ideally overnight, allowing the flavors to meld beautifully.