Welcome to the VMware Communities forum.
You can create a VLAN without SRM. You'll have to configure your network equipment appropriately and then you'll add new virtual machine port groups to your ESXi hosts. You can then register the VMs giving them a different name and start them up in an isolated fashion. When you attempt to register the VMs they'll still have a reference to the production VM port group so you'll want to ensure that you update that before you power them on.