To avoid using VUM or PowerCLI to upgrade your host you can simply use The vmWare online repository.
The commands below have to be executed via SSH (enable this in your security profile and start the SSH server)
esxcli network firewall ruleset set -e true -r httpClient esxcli software profile update -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml -p ESXi-5.5.0-1331820-standard