If you are into your fast food then Bergen has the customary M'cDonalds, Burger King Etc.
Dont think that by going here you will get a cheap meal. They are cheaper than a restaurant but you will still pay around £8 for a Big Mac meal you'd be better off paying a little more and having a decent sit down meal.
If on a budget i found the Bon Apetit chain did very nice sandwhiches.
Favorite Dish: Well up to you really if you like that sort of thing