Preheat oven to 350 degrees F (175 degrees C). Grease a loaf pan with cooking spray.
Place potatoes into a large pot and cover with water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 15 minutes. Drain; mash until smooth.
Combine 1 cup mashed sweet potato, eggs, almond milk, protein powder, coconut oil, and baking soda in a large bowl; mix until well blended. Pour into the prepared loaf pan; smooth the top with a table knife.
Bake in the preheated oven until a knife inserted into the center comes out clean, about 45 minutes.