I mixed up my "buttermilk" and realized we were out of eggs. Oops. I was also out of applesauce.
A quick google search said I could use half a mashed banana. I was actually making a double batch, but I didn't want it to be too banana-y, so I still just used half a banana. Then, afraid it wouldn't be binding enough, I sprinkled in a tbsp of chia seeds over the mashed banana.