Preheat oven to 350F and grease an 8x4 inch loaf pan very well (you can also use 9x5 but your bread will bake faster). If your pan isn't very non-stick, you may want to line the pan with parchment, and grease the parchment.
Grind the chia seed in a coffee grinder or food processor. Transfer to a bowl and stir in the water. Set aside.
In a large bowl, whisk together the almond flour, sweetener, protein powder, coconut flour, baking powder and salt.
Stir in the eggs, melted butter, chia seed mixture, banana extract, and vanilla extract, until thoroughly combined. Stir in the water to thin the mixture to a scoopable consistency. If it's still very thick, add more water, 1 tablespoon at a time.
Stir in the chocolate chips, if using, saving a few for the top of the bread. Spread the batter in the prepared pan and sprinkle the top with the remaining chocolate chips.
Bake 60 to 75 minutes or until golden brown and the top is just firm to the touch. Let cool in pan 20 minutes, then run a sharp knife around the edges to loosen. Continue to let it sit in the pan until cool, about 20 minutes more.
NOTE: The nutritional information includes the chocolate chips. Without the chips, this keto banana bread has 168 cal; 13.8g Fat; 5.3g Carbs; 3.2g Fiber; 6.3g Protein. Storage Information: Store the bread on the counter, tightly wrapped, for up to 4 days, or in the fridge for up to 8 days. It can also be frozen for 3 to 4 months.