In a medium bowl, whisk together all ingredients for the sloppy joe sauce. Set aside.
In a rimmed skillet, brown beef till not longer pink.
Add beef, onion, pepper, and sauce to the slow cooker. Stir to coat evenly.
Cover and set to low heat. Cook 3-4 hours on low. Veggies should be tender.
Serve on buns with toppings of choice.