1 hour glucose test

Tomorrow morning I plan on walking in and doing my 1 hour glucose test. I won’t be doing it until close to 10:30 am. My question is if I stop eating at midnight that gives me roughly 10 or so hours of fasting. If I drink water throughout the night and in the morning will that effect my results? I have an ultrasound in the morning before I do my test and I just don’t think I can last 10 hours without drinking water.

Side note: I had McDonald’s for lunch today and 2 cookies after dinner but ate fairly decent the rest of the day. Should I still be fine? I didn’t have GD with my first born.