Put the vegan mayonnaise, apple cider vinegar, pickle relish, sugar, salt, pepper, and onion powder in a small bowl or jar. Stir well until combined.
Place the cooled macaroni in a large bowl. Add the all of the vegetables and toss to combine.
If you're making the salad ahead of time, keep the dressing and the other ingredients separate, then mix them when it's serving time.
Leftovers will keep in the refrigerator for up to 4 days.