Eat anything you want- just be mindful that you've come so far and you don't want to sabotage yourself. Save some money and don't order anything- just ask the person/people you are with to give you 1 bite of what they have. So, a bite of a hotdog, fries, ice cream-whatever is fine. But try to make good choices, of course. Water instead of soda or juice and veggies/protein instead of fried stuff.
Have fun in the sun! I've not made it to Myrtle this year, weird.