I could eat whatever before the test but as soon as you drink the solution you cannot eat or drink then.

I've never had one but I've had to draw a few, I know you have to fast 12 hr's atleast, might be best to try and plan it so you can go in first thing in the morning because its going to take about an hour and thats a long time not to eat XP. you can drink water tho durring the fast and the test which is very much recommended. theyll take your blood and possibly a urine, give you the drink and a time to finish it (usually 5 min) and then start timing for 1 hr ( or 3 if it's your second test ) and then take your blood again at the end of the hour or each hour. Then you are free!!! :)