You can try this command: C:\Windows\System32\psshutdown.exe -d -t 00
for me this command did sleep the PC using a CMD window.
I also found this command rundll32.exe powrprof.dll,SetSuspendState
in tutorial Sleep Shortcut - Create
for me, this command did a hibernate, and i use Hybrid sleep...
I tried these from "Run..." on the Start Orb, not Acronis.
hope this helps