Depends a lot on your definition of food, but I'd be hard pressed to find an easier-to-construct dessert with as universal appeal as "Rice Krispie Treats":
- puffed rice cereal,
- and a heat source.
Not counting cleanup, takes as little as 3 minutes and a microwave to throw together a small batch, and just about every buffet or cafeteria serving breakfast foods will have the required ingredients. Especially impressive to locals in Eastern Europe and East Asia.