Yes, you really need to do either the teas or the flush. the reason is this, because you are fasting your body is able to work to get out stored toxins in your cells, however unless you eliminate them these toxins will be stored in your colon now and make you sick.
I hate laxative teas because they cramp. what I found works best for me is to do a saltwater flush in the evening. The saltwater will flush gently (relatively speaking) through your system in about an hour. I also do an enema during my morning shower. Neither of these are as bad in practice as they are in theory. just be careful to get the salt water recipe right. the first time I accidently confused tablespoon with teaspoon and I overdosed on the salt which luckily my stomach refused to handle and promptly threw back up.