Black bean burgers are delicious, but they can be a little dry and bland. That's why sauces go so well with them.A good sauce can add flavor and moisture to your black bean burger—and it gives you the opportunity to mix up your meal without having to change your burger recipe.You can put almost any sauce on a black bean burger: ketchup, mustard, barbecue sauce, salsa, guacamole, or even sweet chili sauce (if you're feeling adventurous).The only thing you'll want to be careful of is whether or not your sauce contains sugar or other sweeteners that could mess up the texture of your black bean burger patty.