What foods contain carbohydrates?

It all depends on how you define 'carbohydrates'. Nutritionalists, chemists and the person in the street all have their own definition or even multiple definitions.

As a 'one size fits all' answer, ALL foods contain carbohydrates. All plants produce sugar as a by-product of photosynthesis. (There is as much sugar in a large Apple as in a Mars Bar!) All animals produce sugars to provide energy.