Actually Leah, I'm not surprised you failed if you didn't eat anything yet that day, then had to drink a pure sugar drink and then let yourself sugar crash.
I've never taken it - but I have definitely sugar loaded before I think you should a) definitely eat lunch and b) if you want your best chances of passing, eat something with lower sugar (think veggies as your carbs), higher protein and some fat. The combination of all three helps you to avoid spiking as much - which also helps you avoid crashing as much. A chicken salad with avocado maybe, or a veggie omelet might help. And I would eat it as close to the test as possible so that the sugar from the drink will be balanced by the meal.
I really don't think you should do anything out of the ordinary. Eat what you would normally eat. The point of a non-fasting test is to see how your body reacts to the glucose when you are eating as usual. Don't sweat it!
Mine was at 8:30 am, and I ate breakfast as usual about 45 minutes before: a banana, some peanut butter toast, some juice.
I would try not to eat in the immediate hour before the test, and whatever you do eat, make sure it is protein and fat - no carbs. Eat eggs, peanut butter, etc. Stay away from fruit, or even whole wheat bread... any grain for that matter. Yes, the point is to see how your body reacts normally, BUT do you normally eat a full meal and then follow it up with the world's most sugary drink, probably not real often. Also, if you are "borderline" but still within passing, eating protein over carbs (which will raise you starting sugar) may help you pass the one hour test, so you don't have to endure the 3 hour test.
Now, I know in the past I've eaten a snicker's bar on the way to the test. But, I also know that I've never had anything close to resembling diabetes, so I wasn't worried. Anyhow, if you think you will be borderline on this test, stick with protein and fat!!