Combine the mayonnaise, sugar, and vinegar in a medium size bowl. Set aside.In a large bowl, combine the broccoli, red onion, red grapes, sunflower seeds, and bacon. Add the dressing and combine. (You can eat this right away but I like to make this salad a couple hours in advance and let it sit in the fridge for a couple of hours before serving. It's lets the flavors get to know each other for a bit and makes it extra delish!)