Boil a large pot of salted water over high heat. Add the tri-colored veggie rotini pasta and cook according to package directions, typically 7-9 minutes, until al dente. Drain and rinse under cold water to stop the cooking process.

Chop the broccoli into small florets and finely dice the medium red onion. Set aside.

In a large mixing bowl, combine the cooled rotini, chopped broccoli, diced onion, and shredded mild cheddar cheese. Gently fold together until evenly mixed.

Whisk together the mayonnaise, sugar, and apple cider vinegar in a separate bowl until smooth and creamy.

Pour the dressing over the pasta mixture and stir until evenly coated.

Cover and refrigerate for at least 2 hours before serving to allow flavors to meld.