Any type of broth will work, it just won't pump up the beef flavor in the same way. If you have any dried mushrooms, the liquid from reconstituting those would work. If you have some onions, carrots, and celery (and other veggies) around, you could make a veggie stock yourself by simmering (not boiling, so a bubble or 2 every second) for 45 min-1 hour. To increase the depth of flavor, you can roast the veggies first! If not, water and some herbs and spices will work!