Once you have drunk the lemon water and waited the requisite ten to thirty minutes, you may consume any fruit or vegetable you like, just as long as you juice it—but be sure to juice it yourself. (Bottled or canned juices are not allowed, since the processing removes many of the valuable vitamins and minerals.)
You may also prepare a vegetable soup by boiling pure water (no salt!) and adding fresh, raw vegetables. Speaking of which, you should strive to buy the freshest, organic fruits and vegetables you can find. Organic fruits and vegetables have notably more vitamins and minerals, plus you get the added benefit of consuming food that has not been chemically treated in any way.