Whisk the vinegar and maple syrup with the salt and pepper to make the dressing. Toss the rest of the ingredients with the dressing and chill for at least an hour.
1 tablespoon white vinegar, 1 tablespoon red wine vinegar, 1 tablespoon apple cider vinegar, 1 tablespoon maple syrup, Pinch of kosher salt and pepper, 1 15 oz can of cut green beans, 1 15 oz can of wax beans, 1 15 oz can of kidney beans, ½ Vidalia onion