Arrange bacon in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes.
Drain bacon on paper towels and crumble.
Layer spinach, bacon, eggs, and onion in a large bowl.
Sprinkle with almonds and sunflower seeds.
Whisk vegetable oil, ketchup, vinegar, brown sugar, Worcestershire sauce, garlic, salt, and black pepper in a bowl; pour over spinach mixture and toss.