Yes, you can drink the broth. However, there are a couple of things to keep in mind. First, if you're starting with water and a flavouring mix as your broth, or are using a weak broth, it's not going to be very tasty at the beginning of the cooking process. You will want to wait until you've cooked some of your ingredients before sipping the broth, so it has time to take on some flavour. This is also why some people choose to wait until closer to the end of the meal to add their noodles in (so they can absorb the flavourful stock). You can also wait until the end of the meal to enjoy the broth. Just be aware that it could be very spicy or greasy by the end of the meal, depending on what you cooked.