To hit the sack is to go to bed. Time to hit the sack, hit the sack early, I am going to hit the sack.
It is informal and cheerfully abrupt, and hit the hay means exactly the same thing. To hit the sack is a phrase from a time when a bed really was a sack stuffed with straw.
1phrasehit the sackTo go to bed.
“I'm exhausted, so I'm going to hit the sack early tonight.”
hit the sack is a going to bed.
Also accepted in games: hit the hay
From beds that were sacks stuffed with straw or hay.
A reference to the manner in which farmers tend to sleep on sacks of hay.
Etymology from Wiktionary, CC BY-SA
Practised in Idioms