To sleep like a log is to sleep so deeply that nothing wakes you. I slept like a log.
It reports the quality rather than the length, since eight bad hours do not count. The log is chosen for being still rather than for anything else.
1phrasesleep like a logTo sleep so deeply that nothing wakes you.
“After a day on the hill they all sleep like a log.”
sleep like a log is a phrase.
Practised in Idioms