From inside “C:\Program Files (x86)\VMware\VMware Workstation” (Windows default installation location), or wherever your installation is on Linux or Windows:

vmware-vdiskmanager.exe -r 'source.vmdk' -t 5 'destination.vmdk_stream.vmdk'

‘-t 5’ is where you specify the stream-optimized format for example, here are all available types:

0 : single growable virtual disk
1 : growable virtual disk split into multiple files
2 : preallocated virtual disk
3 : preallocated virtual disk split into multiple files
4 : preallocated ESX-type virtual disk
5 : compressed disk optimized for streaming
6 : thin provisioned virtual disk – ESX 3.x and above

Enjoy!