Preheat oven to 350 degrees F (175 degrees C). Prepare a loaf pan with cooking spray.
Beat sugar, banana, and yogurt together in a large bowl until smooth. Beat 1 egg into the banana mixture until smooth before adding the second egg and beating again until smooth.
Mix all-purpose flour, chickpea flour, baking soda, ground cinnamon, and salt together in a separate bowl; add to the banana mixture with the water and beat until smooth and batter-like. Stir mashed sweet potatoes into the batter until smooth. Fold chocolate and chia seeds through the batter; pour into the prepared loaf pan.
Bake in the preheated oven until a knife inserted into the center comes out clean, about 1 hour. Cool in the pan for 10 minutes before slicing.
