Hi, My advice, based on breaking The Master Cleanse fast would be to prepare some vegetable broth using high potassium veggies like unpeeled potatoes, carrots, onions, Celery and parsley. Gently simmer the vegetables in filtered or distilled water until very tender and drink the broth. On the next day throughly blend the cooked veggies and add them to the broth making a kind of creamed soup. This low fiber, high mineral broth/soup is an excellent way to break a fast and resupply vital electrolyte minerals. It should not cause any cramping like high fiber raw fruits might. You can also add some brown rice or oatmeal the second day for additional energy, avoid milk, Sugar and fats for a few days. When you start feeling stronger you can add some raw fruit to get your digestive system in higher gear. Some people can break their fasts with almost any food, but others must do it slowly and gently. I have broken short (48 hour) fasts with Watermelon before, but it may have to much fiber for you.
Congratulations on your five days. I hope this one unpleasant experience doesn't keep you from fasting in a safe healthy way.