If using dried pinto beans, rinse the beans and place in a 4- or 5- quart Dutch oven. Cover with 2 inches of water and add the salt. Bring the pot to a boil, and let the beans boil for 15 minutes. After this time, cover the pot and turn the heat down to low. Simmer the pot covered for 1 hour and then remove the lid. Continue to simmer the beans until tender and soft, which can take anywhere from 30 more minutes to 1 1/2 hours, depending on the age of the beans. (If the water gets too low, add a little more to the pot). When the beans are tender and soft, drain the beans.
If using canned pinto beans, simply drain them.
If using a slow cooker, place the cooked beans into the slow cooker. If using the oven, preheat the oven to 350°F, and place the beans back into the Dutch oven.
In a skillet, on medium-low heat, cook the bacon about 5 minutes, turning once. You want to render some of the fat from the bacon but leave it undercooked and still floppy. Remove the bacon from the skillet with a slotted spatula, and place on a paper-towel lined plate leaving the rendered fat in the skillet. When cool enough to handle, chop the bacon into 1/2-inch pieces.
With the skillet still heated on medium-low, add the onion and cook until translucent, about 5 minutes. Add the garlic and cook for 30 more seconds. Turn off the heat.
Spoon the onions and garlic over the beans, either in the slow cooker or the Dutch oven, then deglaze the skillet with the Dr Pepper by pouring it into the skillet and then swirling it around while scraping the bottom. Pour the Dr Pepper over the beans.
Add to the slow cooker or Dutch oven the bacon, ketchup, molasses, apple cider vinegar, chili powder, smoked paprika, black pepper, and cayenne. Stir everything together until well combined then taste and add more salt if needed.
If cooking in the slow cooker, cook covered on low for 8 hours or high for 6 hours. The beans will be a little soupy so if you prefer a drier consistency, you can remove the lid for the last hour. Because flavors can get muted in the slow cooker, you may want to taste and add more seasonings and perhaps a splash of vinegar at the end to brighten up the dish.
To cook the beans in the oven, cook covered for 1 hour, then remove the lid and cook uncovered for 1 to 1 1/2 hours, depending on how dry you want your beans. Again, feel free to taste after cooking and adjust the spices and add a splash of vinegar if you like.