Preheat oven to 400 F.
Wash sweet potatoes and pierce each with a fork all around, about 5 times.
Place on a baking sheet and bake until tender, about 45-60 minutes.
In a large skillet over medium heat, cook the ground beef until done, about 10 minutes.
Add the celery, carrots, bell pepper, onion and garlic to the ground beef and cook down for another 8 minutes.
Add in the remaining ingredients and stir to combine. Reduce heat to low and cover. Cook for 25 minutes, stirring occasionally.
When the sweet potatoes are done, remove from the oven and let sit to cool until they can be handled.
To serve, cut a sweet potato in half, not cutting all the way through, and open by pinching the ends towards each other. Loosen up the potato inside with a fork. Spoon the sloppy joes mixture over the top and serve.