Add the navy beans to a large bowl and submerge them in water. Cover and let the beans soak overnight.
The next morning, drain the beans, and add them to a large pot. Submerge again with water and bring to a rolling boil over high heat. Reduce the heat to a simmer and cook for 45 minutes. Drain and set aside.
To a large skillet, add the bacon and cook over medium heat until crispy, about 8-10 minutes. Remove from heat and transfer to a plate that has been lined with a paper towel. Leave the bacon grease in the pan. Set the heat over medium heat once again, and add the onion. Cook the onion until tender, about 5-6 minutes and then add the garlic. Cook for an additional minute or until fragrant.
To a slow cooker, add the root beer, barbecue sauce, brown sugar, ketchup, honey, Heinz Yellow Mustard, apple cider vinegar and maple syrup. Whisk until combined. Add the beans, bacon and onion/garlic mixture to the slow cooker and stir to coat. Cook the beans on low heat for 8-10 hours or until tender and thickened. Serve immediately or refrigerate for 12 hours, and reheat in the slow cooker. By waiting 12 hours, allows the bean to thicken substantially. They are much better the following day.