Albert Barnes Commentary Psalms 78:65

"Then the Lord awaked as one out of sleep, Like a mighty man that shouteth by reason of wine." — Psalms 78:65 (ASV)

Then the Lord awaked as one out of sleep—literally, as one sleeping; that is, as one who is asleep suddenly arouses himself. The Lord seemed to have slept, or to have been inattentive to what was occurring. Suddenly he aroused himself to inflict vengeance on the enemies of his people. Compare Psalm 7:6 (see note) and Psalm 44:23 (see note).

And like a mighty man—the allusion is probably to a warrior.

That shouteth by reason of wine—the proper idea here is that of singing, or lifting up the voice in exultation and rejoicing; the idea of a man who sings and shouts as he is excited by wine, and as he presses onward to conflict and to victory. It is not uncommon in the Scriptures to compare God, as he goes forth to accomplish his purposes on his enemies, with a warrior. See Exodus 15:3 and Psalm 24:8.