Fasting can be beneficial, but you don't need some special drink that BB (or anyone) is selling to get your eating back in order. In fact, if you feel you have to rely on a fast to counteract whatever bad eating habits you have developed, it seems close to an eating disorder to me. Clean up your eating using REAL FOOD, that contains real nutrients, not some Slim-fas- like drink mix that probably contains lots of synthetic vitamins and mineral, as well as who knows what artificial sweetener). (There are a few...and very few...beverage mixes that are whole-foods-based meal replacements and would be considered foods and not the same as slim fast. "Vega" is one example.)
Instead of a fast, you could do a 'relative fast' (I've discussed this before, and you can find a thread or two by searching for the term using advanced search, looking for it in Open Discussion under "message"). A relative fast is eating a step (or several) cleaner than you normally would.
If you eat a SAD (standard American diet...an a propos acronym!), then going for a few days eating a vegetarian, whole-foods diet would be a relative fast. If you are vegetarian, then doing a primarily raw vegan diet for a few days would be a relative fast. If you're a raw food vegan, then a juice fast or juice and water fast would be a step up.