Follow these steps to update a template in vSphere.
1. In vSphere, right click the template to “Convert to Virtual Machine”
2. Do changes – Install updates, push over new scripts, whatever changes you need done to the template.
3. When done, just right click “Convert to Template”
It really is that easy.
But lets say you have a Server 2016 / SQL 2014 template and you want to make a Server 2016 / SQL 2016. You would follow similar steps:
1. Clone the Server16SQl14 template to a new template and give the clone an name like Server16SQL16.
2. Convert the new Server16SQL16 template into a temporary test VM.
3. Setup SQL Server install files or whatever changes you need from SQL 14 to SQl 16.
4. Convert back to a template.