Can someone please explain this: 都没吃饭吗
It means the coach thinks the players are not energetic enough as if they were hungry.
This sentence can only be used in some situations:

a coach blames the players being not energetic enough
an officer blames the soldiers being not powerful enough
fighter ridicule the opponent being so weak

or similar. Always considered as a blaming or ridiculing.
If you ask a friend about eating, it would be “吃饭了吗？” instead of “没吃饭吗？”.