Login on vSphere Client against your vSphere host
Look for your host machine
Then go to Summary and check Host: (ESXi IP)
Now start a new vSphere session (on the same machine or on another) to reach that IP login on that ESXi host.
When you are in, look for host machine again what should found somewhere on this host.
When you found it
There is two ways to go now
1. right-click and pick guest reboot (a simple reboot might not be good options).
2. Open Console on that machine, Press F12
Then Press again F12, now you probably need to log in with a root account.
After having login with the root account.
Press F11 reboot