Sonderkommando
The Nazis needed the Sonderkommandos to stay strong enough to work.  Because of this, they were treated a little better than the other prisoners.  They were allowed to sleep in their own barracks.  They were also allowed to keep things like food, medicines, and cigarettes that had belonged to people who were killed in the gas chambers.  The Nazis allowed these things because they wanted to be able to kill people as quickly as possible in the gas chambers.  Without the Sonderkommando to help with the dead bodies, the Nazis would not be able to use the gas chambers as much.