For mine I was told I wasn’t allowed to have anything to eat or drink that morning. Mine was the one hour test with each child.
If you’re unsure what you can and can’t eat call your doctor I was told you can eat a sandwich or small breakfast no cereal nothing containing sugar that’s for the 1 hr test.Nothing at all for the 3 hr test you’re fasting.
Go first thing in the morning and just have a hard boiled egg or two with water—- or other protein, avoid carbs/fruit/juice. Make sure your phone or tablet is charged so you can be entertained during the hour you wait. Then get yourself a nice treat (I recommend something sugary from Starbucks) after and relax.