I wouldnt trust grape juice for more than 2 days.Thats a fermenataion factory(yeast overgrowth) waiting to happen. Grape juice is highly fermentable. There is really nothing in grape juice thats anti-candida or winemakers would have a hard time to get it to ferment.
The mccombs library is a good place to start. Dr. Jeff has much science available concerning candida. A lot of specialists are trying to promote their products so you have to be careful with what you read. Sometimes you have to filter all the non-sense and try to figure out what will work best in your situation. Some of the programs might work for some people , whereas other programs will not work for more complicated ones. Diet can really vary depending on the individual. Thats something that the individual has to work with to figure out what works best for them.
I dont always trust studies that have been clinically tested because even those can be done in a isolated or manipulated environment. But they can give you some direction or ideas with what might help. And what happens in lab and the human body can be somewhat inaccurate. Its not easy because candida is not recognized and researched like it should be.