If you don't use the Update Manager you can install the updates via command line as well.
http://blogs.vmware.com/vsphere/2012/02/quickest-way-to-patch-an-esxesxi-using-the-command-line.html
gives you an overview how to do it with vCLI or direct shell access
if you have esx and not esxi installed you can follow this explanations here:
http://communities.vmware.com/people/vmroyale/blog/2009/10/12/single-use-esxupdate-how-to-for-esx-4