Grey of colour, spheroid of shape, devoid of taste and doughy of texture, ration spheres are a cheap food product nearly ubiquitous among space travelling vessels, if only as an emergency supply.
Also known as 'nutrient spheres' or 'nutrient supplements', one will be a satisfactory meal for most non-humans. Humans, however will require four or more per sitting (enhanced humans will require far more).
The spheres will supply almost all of a human's dietary requirements, though several mineral supplements will be required for long-term health, calcium in particular. (Rat in Sheep's Clothing)
A similar product is the 'meal tablet', a somewhat smaller product, though one will still prove a meal for a Corti. Twelve (possibly more) were required for 'the morning' by Adrian Saunders, post enhancement. (Salvage 02 - Food)