In my Windows 10 laptop, there is Sleep mode, but I had to re-enable this feature first.
To enable it:
1. type "Lid" in your Start Menu, then click on "Change what closing the lid does". You will be brought to a System Settings Page.
2. In that page, click on "Change settings that are currently unavailable".
3. Scroll to the bottom of the page.
4. Make sure that "Sleep" is checked so that it will be shown in the Power Menu.
However, you may want to be cautious in using Sleep Mode for Windows 10. Unlike Windows 7, sleep mode turns off the hard drive making the laptop safe to move and transport. But in Windows 10, it seems that the hard drive doesn't turn off completely, making it unsafe to transport or move the laptop (risking damaging the HDD).