Eating before a blood test?

I'm so afraid to faint. Could care less about the needle, blood or pain.. but am terrified of fainting. I keep reading to eat sugary foods and drink lots of water before, but anyone I've known who had a blood test had to fast, couldn't even drink water for like 12 hours before. Ahh! Are there certain foods you can eat ? Will they let you eat a little if its almost a guarantee that you will pass out, I get dizzy so easily. Honestly won't even make it through the first 5 hours of fasting let alone the next morning and then losing blood. If I don't eat a good breakfast in the morning and have fruit or something with sugar I almost pass out every day. How am I gonna do this ???