In a large pot or Dutch oven over medium heat, cook 6 slices thick-cut bacon until crispy, about 8–10 minutes. Remove bacon and drain on a paper towel-lined plate, leaving about 2 tablespoons of fat in the pot.
Add 1 large chopped yellow onion to the pot and cook over medium heat for 5–7 minutes until softened and translucent. Stir in 2 minced garlic cloves and cook for 1 minute until fragrant.
Pour in 2 (15-ounce) cans rinsed and drained pinto beans, 1 cup ketchup, 0.5 cup packed light brown sugar, 2 tablespoons yellow mustard, 1 tablespoon Worcestershire sauce, 1 tablespoon apple cider vinegar, 1 teaspoon chili powder, 0.5 teaspoon smoked paprika, 0.5 teaspoon salt, 0.25 teaspoon black pepper, and 0.5 cup water (or beef broth). Stir to combine, bring to a gentle simmer, then reduce heat to low, cover, and cook for 30–60 minutes, stirring occasionally.
Crumble the cooked bacon and stir most into the beans, reserving a little for garnish. Taste and adjust seasoning if needed. Serve the cowboy beans warm.