If it is meat brine, discard it. It is not recommended to reuse it.
Sauerkraut juice is a great natural brine which is loaded with bacteria. Use it next time to jump start fermentation. reusing a part of product for making a new batch has been practiced for centuries. Bread, cheese, meat, sauerkraut, any naturally fermented product can be used whether it contains brine or not. This practice is called back slopping.
I like to use some in my salad dressing, as an option, when I have extra. Salad dressing consists of: red wine vinegar/cider vinegar, pickle juice, garlic, dill, water, sugar, maggi flavoring, w/ other options like Dijon mustard, lemon juice, brine,etc. in a 1.5 Qt. container, olive oil and spices added separately.