Overripe bananas are always best when making banana bread. I didn't need to use too much sugar because of it. Add more sugar, about 1/4 cup if the banana that you have is not overripe.
Chocolate chips and blueberries are my absolute favorite add-ins but you can also use nuts and other berries. I keep these in the fridge, stored in an airtight container (or ziplock), for a maximum of one week.
I use a mini-toaster to reheat at 120c and it restores the crunchy texture of the topping.