I did not fast (as per the dr's instructions) but I wondered the same thing, since I had heard of most people
fasting. I did try to cut back on sugar/carbs that day. I ate protein on a wrap for lunch, which was the last thing I ate before drinking the drink, etc. I passed, and most of my friends failed who had to fast! Not sure if that was a coincidence, but I'm happier eating than fasting ...