The problem with doing the Master-Cleanse with bottled juice is that it's been pasturized and the enzymes are dead. Enzymes die at tempertures greater than 120.
I don't understand why someone would be bothered by sqeezing the lemons. The recipe is not that hard to do and is less time consuming than preparing regular food. It takes me about 5 minutes to squeeze enough lemons for my lemonade for the day. I squeeze the juice by hand and what I don't use right away goes in a seale jar and into the fridge. I start every morning with fresh squeezed juice.
I'm often amazed at how people try to find short cuts to something that is already so simple. What's so difficult about reading the instructions and then following them?