Cryo berths are used to transport cryogenically frozen citizens aboard a spacecraft from one city to another. Unlike normal passengers these "cryo travelers" will not pay for being transported, and they do not bring any belongings or money with them on the trip.
These are generally used to transfer hundreds or even thousands of citizens between cities at a time.
Unlike other types of berths, they are not physical objects placed in a spacecraft design, but are simply allocated as a percentage of hull volume.
Cryo travelers can be awoken mid journey and recruited as crew, troops, or even normal passengers. When awoken they will however be naked with no belongings or money, so cryo travelers awoken to the role of passenger will still not pay for the trip, and a cryo traveler awoken as a troop will have no weapons or armor.
Furthermore, cryo travelers recruited as crew or troops will be unskilled, starting them at rank 0 instead of rank 1 of their given assignment, and thus they will perform worse than regularly hired crew.