The Chinese Takeout item is cold, Asian-style noodles contained in a box from a Chinese restaurant. As it is unlikely that the Combine manufactures these and due to the extended period (10-20 years) that the Combine has controlled Earth, these noodles are more than likely long past the expiration date.
Like all food not produced by the Universal Union, Chinese Takeout is classified as contraband and will warrant punishment from the MPF if a citizen is caught carrying it. The severity of punishment, however, depends entirely on the regulations the city administration has on consumable contraband.
The Resistance, which obviously ignores regulations, makes frequent use of Chinese Takeout along with other contraband, as it is a better, if unsatisfying, alternative to the Universal Union-produced consumables, which contain memory-erasing chemicals and other negative additives.
Chinese Takeout can be eaten by either clicking on if it is in the player's inventory or using the action key (default "E") on it if in the game world. From there, the option "Eat" must be selected, and a chewing sound will accompany a health restoration of 5 units.