no coconut water, if you want to technically stay in the fast. however if it makes adherence a lot better for you then a small amount of calories like coconut water or bone broth is okay. It’s ultimately about what you can stick to.
If your refeed was clean and ideally low-carb/keto you should stay in ketosis basically the whole time. It also makes the next fast easier as your energy levels will stay stable. Just keep your electrolytes up.