The animal that can go the longest without drinking water is the kangaroo rat. The kangaroo rat can live for years without water if it has to.
Kangaroo rats are common to the deserts in Mexico and the Southwestern United States. They can survive up to 5 years without drinking water and have learned some interesting adaptations that allow them to live in one of the driest environments on the planet.
Kangaroo rats build deep burrows underground in humid areas so they lose less water when they breathe. They seem to acquire all the moisture they need in the foods and seeds they eat. They also develop an oily layer on their fur that keeps moisture locked into their skin for extended periods of time.