Bratwursts should be cooked on a stove top for about 5 minutes. They should be cooked until they are brown on the outside.
Cooking time depends on how the brats are stored. Keeping them in the refrigerator before cooking lessens cooking time -- they cook in 5 minutes when sauteing them whole in a pan. However, if the brats are frozen, it will take more time until they are cooked through. Brats can also be grilled, broiled and boiled.
To enhance the flavor of brats, many people will first boil them in beer. To do so, empty a can or bottle of beer in a pan and drop the brats in. Boil the beer and cook until the brats become plump. Then, cook on a stove top per usual until browned on the outside. Cooking brats on the grill helps enhance the overall flavoring.