What happened if Jews didn't do work in the labor camps?

They would have been forced to work...if they did not, they would have likely been killed by a guard.

___

I knew a man - a non-Jewish German - who was a prisoner at Dachau. One day in the summer of 1942, when it was very hot, an SS guard accused him of not working properly. Thereupon the guard flew into a rage and punched the prisoner hard in the face several times, knocking out several teeth.

Getting the prisoners to work was not difficult.