enable shell and ssh on esxi
press alt + F1 to login into shell
find the vmdk file most likely in vmfs/volumes/datastore1/myvm.vmdk
then type in this command:
vmkfstools --punchzero myvm.vmdk
press alt + F1 to login into shell
find the vmdk file most likely in vmfs/volumes/datastore1/myvm.vmdk
then type in this command:
vmkfstools --punchzero myvm.vmdk