In a medium jar, combine olive oil, white vinegar, sugar, kosher salt, and fresh ground pepper. Seal tightly and shake for 30 seconds.

Slice sweet onion into thin half-circles and set aside.

Drain and rinse the five cans of beans. In a large mixing bowl, combine the beans with sliced sweet onion.

Pour the dressing over the bean mixture and gently fold to coat the ingredients evenly.

Cover the mixing bowl and refrigerate for at least 6 hours or overnight.

Let the salad sit at room temperature for 15 minutes before serving.