beauty sleep
From Longman Dictionary of Contemporary Englishbeauty sleepˈbeauty sleep noun [uncountable] SLEEPenough sleep to keep you healthy and looking good – used humorouslyExamples from the Corpusbeauty sleep• A girl needed her beauty sleep.• She started her new job on Monday and she said she needed her beauty sleep before tackling the front attic.• Playing Desert Storm on my Sega console had not only eroded my morals, it had disturbed my beauty sleep.• I didn't get my beauty sleep last night.