Probably the exact same thing they eat every day.
Traditional food is corn beef and cabbage. But some people dye whatever is on hand green, or make the corn beef and dye it green.
In many places, lots of food and alcohol. In others, nothing specific because they may not recognise St Patrick's day as a celebration.
Anything that is green.
Booty
Traditional food on saint patricks day is cabbage with either ham or bacon and , of course, beer.
food
chinesse food
Any food that French people eat basically.
turkey
rice
olives
bugs
frogs legs
Noodles :S
Food shortages
Hot Dogs