A.T. Robertson Commentary 1 Thessalonians 5:7

"For they that sleep sleep in the night: and they that are drunken are drunken in the night." — 1 Thessalonians 5:7 (ASV)

They that be drunken are drunken in the night (ο μεθυσκομενο νυκτος μεθυουσιν). No need of "be" here, they that are drunken. No real difference in meaning between μεθυσκω and μεθυω, to be drunk, except that μεθυσκω (inceptive verb in -σκω) means to get drunk.

Night (νυκτος, genitive by night) is the favourite time for drunken revelries.