Bring a large pot of salted water to a boil. Cook the elbow macaroni according to package instructions until al dente (usually 7-8 minutes).
Drain the macaroni in a colander and rinse thoroughly with cold water to stop the cooking process and remove excess starch.
Allow the macaroni to drain completely, tossing occasionally to release excess water.
In a large mixing bowl, combine mayonnaise, white vinegar, sugar, salt, and pepper. Whisk until smooth. If using condensed milk, add it now and mix until completely blended.
Add the cooled macaroni to the dressing mixture and fold gently until evenly coated.
Fold in the carrots, peas, sweet pickle relish, and shredded cheddar cheese. If using optional ingredients like ham, raisins, pineapple, bell pepper, or chopped eggs, add them now and mix gently.
Taste and adjust seasoning as needed, adding more salt, pepper, vinegar, or sugar to achieve your desired flavor balance.
Cover and refrigerate for at least 30 minutes, though 2-4 hours is ideal to allow the flavors to meld.
Before serving, stir gently to redistribute the dressing. Serve chilled.
