If you trim the brisket correctly, the fat and water will do the same as broth. If you're oven-baking the brisket, you can add some beef broth, chicken, or vegetable stock to add some flavor. I love a combination of worcestershire sauce, liquid smoke, and some beer; it'll keep the brisket from drying out and enhance the flavor. If you smoke the brisket, you will not add broth to it.