The giants of alter egos of Stone gods were given the nutrition by the juice(the soup) which come out from the holes of the bodies of Stone gods.
The giants had the tubes on the back of the neck and they got the nutrition by inserting them into the holes of Stone gods.
You can find the images of Stone men with tubes on the head in the below site.
http://slicer93.mbsrv.net/5-128.html
http://slicer93.mbsrv.net/iwae10.jpg