Vegetable broth adds a depth of flavor that water doesn't, but here are some options if you don't have broth. Use water with a bay leaf, garlic clove (or garlic powder), salt, and black pepper. A tablespoon of soy sauce and/or a teaspoon of miso paste or tomato paste can also be used to lift the flavor. A tablespoon of vegan soup stock is another option that can work for this stew.