A drunk tank is a jail cell

Prison cell

A prison cell or holding cell or lock-up is a small room in a prison, or police station where a prisoner is held.Prison cells are usually about 6 by 8 feet in size with steel or brick walls and one solid or barred door that locks from the outside. Many modern prison cells are pre-cast. Solid doors...

accommodating, customarily or as a temporary expedient, at least one person who is intoxicated, especially with alcohol.

Traditionally, and in some jurisdictions currently, the circumstances of drunk-tank occupants may vary widely, as to whether in fact intoxicated, whether willingly there, whether isolated to protect them from others, confined to protect others from them, or simply permitted to find shelter, and whether legally under arrest, charged with an offense, or neither.