I had a similar question and it seems that Central Diner no longer exists. However, TWA Hotel now has a few food options open 24 hours (Corner Store, Coffee Shop, Vinny's Panini), and the Sunken Lounge serves food and drink until 11 pm or 12 am depending on the day of the week. This is probably now the best shot after hours, unless you are inside T4 in which case you have a 24 hour McDonalds.