I never heard of those and haven't looked them up. My thought is that it is probably just brewer's yeast or tomato juice or some mixture like that. I personally don't like the idea of altering the dog's diet for something like this. Instead I would recommend either watering the area well after each pee or adding lime to the area. Since you say she goes in the same place, lime would be my first thought. Lime will simply change the pH of the soil so that the urine will not burn the grass. If you decide to just water the spot each time, you need to use a good amount of water. If you use too little then the spot will turn a dark green. This might be a good thing, but it will make the lawn look uneven. Again, since she goes in one spot this might not be an issue. I have a friend whose grass has dark green patches throughout the yard and it looks odd. Especially with the occasional brown spot.
Edit: there are also products like "dogonit lawn treatment spray" that I have heard of but never used.