Barley water

Hi Mamas! My little one is turning 11th months in few days time. She is currently having constipation issue i guess (always cry when she poop) so our parents have advised us to give her barley water. As it gonna be tasteless, i believe my LO will reject it since she doesnt like to drink plain water hence, would like to check if rock sugar is recommended to add into barley water? Thanks in advanced!