Ration bars are similar to energy bars, and are eaten by soldiers in the Horde.
Ration bars come in two varieties — gray and brown — and they are presumably the only sustenance that cadets and soldiers receive. It can be assumed that they are rather tasteless. They also have a gooey kind of texture, as seen when Kyle dropped Adora's birthday cake, causing them to splatter on the ground.
In the episode Remember, Kyle, Lonnie and Rogelio make a "cake" out of Kyle's grey ration bars to celebrate Adora's successful first mission with the Horde. Adora states, in her appreciation for the gesture, that the "gray kind is way better than the brown kind."
In Fractures, Scorpia is confused and even a bit frightened when she was offered a salad for the first time. This shows that some inhabitants of the Fright Zone may have never eaten anything other than ration bars, or ever even known about other types of food.
Both Adora and Catra like the gray ration bars much better than the brown ones. This is a bit of a running joke throughout the series, as neither option seems appetizing.
In the Season Five episode "Corridors", during a flashback scene with Adora and Catra as children, Adora finds Catra hiding behind a stack of boxes in the hallway, and, in an attempt to draw her from her hiding spot, says: "Catra it's dinner time, and you're missing it! It's the gray kind tonight, I know it's your favorite."
In "Beast Island", King Micah said that his ration bars were stolen by Entrapta, though how he managed to retrieve some in the first place is unknown.
- Season Four Episode 12