I am novice to water fasting. I did my first five days Water Fast
a couple months ago. Imagine five days and it took me about a week of re-feeding period to get well and back to normal.
Beside drinking orange juice, vegetable and fruit juice the vegetable soup more like vegetable stew helped me much.
Garlic, onion, ginger, turmeric powder, cabbage, Kale, broccoli, sweet potato, pulps of the vegetable juice like carrot good to thicken the soup and good home made chicken stock. Do not over cook it. Just boil it for 2-3 minutes and turn off the heat. Let it rest for 10 –15 minutes, good to go. This soup/ stew saved my life and nourished my body and soul. This veggie stew tasted fabulous just like a thanks giving feast.
On the last day of my fasting (the fifth day) I though I was dieing.
Mind yours was 18 days. I think you need more re-feeding time than mine.
Good luck and do not worry.