Arrange sliced sweet potatoes on a cutting board and trim any uneven edges for uniform thickness.
Heat the cast-iron skillet over medium heat and add the soy sauce, allowing it to warm and coat the surface.
Place the sweet potato slices in the skillet in a single layer, pressing down slightly, and cook until edges are golden brown and slightly crispy, about 4-5 minutes per side. Use tongs to flip and ensure even caramelization.
Remove the caramelized sweet potatoes from the skillet and set aside. Wipe the skillet if necessary, then warm the tortillas in the same pan for about 30 seconds per side until pliable.
Lay a tortilla flat, arrange a few sweet potato slices in the center, add hot sauce and cheese if desired, then fold the sides over and roll up tightly into a burrito.
Optional: Return the burritos to the skillet for 1-2 minutes per side to crisp the outside and melt the cheese, then serve immediately with additional hot sauce.