Any simple ways to increase humidity in a small space?

i am looking for a simple way to increse the humidity in my grow cab, its a very small space about 1.5x4, the humidity is way to low, i have the temp at about 80 degrees but does anyone know of any easy ways to increase it?? the reason im looking for easy is bcuz i have my grow room built im jus doing the last things to it, and im veggin my mothers in a cabinet-

A bucket of water.

thanks guys! but i finally asked my mom and she actually had a humidifier!