Spinach Watermelon-Mint Salad

1 cup apple cider vinegar

¼ cup Worcestershire sauce

½ cup vegetable oil

1 tablespoon sesame seeds

1 tablespoon poppy seeds

¼ cup white sugar

1 (10 ounce) bag baby spinach leaves

2 cups cubed seeded watermelon

1 small red onion

thinly sliced

1 cup chopped pecans

toasted

1 cup mint leaves

finely chopped