What's the best thing to eat if you feel like you're going to pass out?

I'm getting a tattoo...I'm a bit nervous that I'll pass out though. I want to be prepared and bring a snack. I'm having trouble deciding between: a granola bar, a chocolate bar, or lollipops. Which might be the best/quickest way to prevent passing out? Please only answer if you know from experience, DON'T guess.