Go to settings > focus mode, then tap the top right corner, tap sleep, and then tap custom focus mode.
Customize your focus mode. For example, you can allow important people to contact you, customize the lock screen and home screen, and customize the behavior of applications and iPhone when Sleep focus mode is turned on.
Tap Schedule or Automation, then tap Add Schedule or Automation.
Select "Based on Schedule", and then enter the time period for your lunch break.
Click Finish, and then return to the focus mode interface.
In this way, when you enter the lunch break, the iPhone will automatically turn on the "sleep" focus mode to record your sleep data. When you finish your lunch break, the iPhone will automatically turn off the "Sleep" focus mode and display your sleep report.