While fasting a few days a month is always a good thing for maintenace I would not expect any real cleansing from it.
This not to discourage you from trying it. Even the very fact that you're making an effort to rid yourself of cravings can itself be a factor in keeping the cravings away. Nothing to loose I say. Give it whirl and let us know how it works for you.
Something that really helps to keep the system clean is drinking 1/2 oz of water for every lb of body weight daily.