Odwalla and Naked are fresh pressed - flashed pasteurized foods. I've read that most of the enzymes are destroyed during the flash process. Maybe some vitamins and some enzymes survive - but they are weakened or diminished as it sits on the shelf. They are much better to drink than say ocean spray or tropicana which are from concentrate and fully pasteurized and all the good stuff has been strained out of em - and some of those juices have a shelf life of fooooreeeeverrrr.
The best way is to juice yourself. I know the juicer is expensive. I did odwalla and naked when I was trying to go raw. But I wouldn't fast on it. It's not that great for you.
Try the lemonade fast - you don't need any equipment...