since ESXi 5.1 it is no more possible to create or clone a disk by using the 2gbsparse disk format. Because it is not supported as a VMFS vitual disk format. This disk format is only part of the Desktop Products of VMware, like VMware Workstation or VMware Player.
However in earlier version the command line tool vmkfstools could create disks and clone disks in such format. If you try this in ESXi 5.1 or later version a
~ # vmkfstools -i Disk.vmdk clone.vmdk -d 2gbsparse “The system cannot find the file specified.”