The phrase "how did you sleep" in Spanish can be translated as:

• ¿Cómo dormiste? (informal singular, used with friends or family)
• ¿Cómo durmió? (formal singular, used with someone you address formally)
• ¿Cómo durmieron? (plural, when asking multiple people)

These are the most common and direct ways to ask this question in Spanish depending on the level of formality and number of people addressed.