See here:
http://www.landships.info/landships/...Anti_Tank.html
They would have been the WW1 variant of the Stielhandgranate (M1916) but I think they had pretty similar performance. Basically, throw a bag of grenades (or a bundle from 1918) either onto the top of the tank or under a tread, and you could expect to disable the tank. No details on the actual damage done to the tank however.