>ALL< bottled juices have to be heated to kill bacteria (Pasteurized) by law. The heat also kills the live enzymes also. Add to that any other porcessing and how long the bootle has been on a shelf and you pretty much wind up with something pretty much devoid of any nutritional value. Also if it's not organic god knows how many toxic contaminants the juice contains. Since the whole purpose of the Master-Cleanse is to rid your body of toxins this bootled juice is pretty much defeats the purpose of the MC.

Bottled lemon juices have been heated to high temperatures to kill the enzymes and preserve the freshness of the juice. However, it is the live active enzymes that are an essential element in the cleansing aspect of the Master Cleanse. The enzymes help digest and loosen the mucoidal mass lining the intestines. (the cayenne pepper does this too, but through a chemical reaction, not enzymatic).
I suppose anyone doing Master Cleanse simply for weight loss could use bottled juice; but since this is intended to be a cleansing protocol live enzymes are absolutely essential for The Master Cleanse to be successful.