One scene that I really remember is the ‘guards’ making a prisoner dig a trench in the camp in blistering heat. When he had dug it, they made him fill it in again straight away. I’ve watched a few films about PoS camps and I cannot remember which one this was. Thanks
Could it be:
Cool Hand Luke (1967).
“As further punishment for his escape, he is forced to repeatedly dig a grave-sized hole in the prison camp yard, fill it back in, and is then beaten.”