Apollo 13's lunar module Aquarius was designed to support two men for two days but had to support three men for about four days, during which the crew reduced water consumption to six ounces per person per day, one-fifth of normal intake.
Sources
- Apollo 13: Mission Details - NASA (nasa.gov)
- https://spacecenter.org/apollo-13-virtual-exhibit/ (spacecenter.org)
- https://www.lpi.usra.edu/lunar/missions/apollo/apollo_13/ (lpi.usra.edu)