While adding a considerable amount of Radiation, it restores one of the highest amounts of Hit Points among the food items. According to Kai, it mostly consists of trog meat mixed with the irradiated water from the three rivers in The Pitt. That would make consuming it amount to cannibalism, as trogs are former humans that have succumbed to the environmental conditions in The Pitt. She also implies upon serving slop that "it's your funeral".
It uses the Pipboy icon and world model of noodles.
With its extreme radiation for a consumable, it would take a mere 40 servings of slop to kill you (at near zero radiation resistance).
Kai is the only source of slop in the game. If you are a collector of rare/unique items it is advised to acquire at least one 'slop' before completing the quest Unsafe Working Conditions and talking to Midea about fighting in the hole, as she will no longer serve you after Ashur's speech.