The steps to install ArcGIS Enterprise with the Application Builder is well documented already, and have successfully used this to install both 10.5 and 10.6 on several machines both virtual and physical.
However, I do understand that moving from a standalone GIS Server to a full stack is a bit of a jump, especially for those of us in GIS that may not have much experience in IT (e.g. me)
From what you have mentioned, I believe the issue you are having is that although the Virtual Machine is Windows Server 2016, it is not setup on a domain and therefore does not have a fully qualified domain name (requirement).
A few options, and this is really more on the IT side of the prerequisites for ArcGIS Enterprise.
You need to have a fully qualified domain name in order to successfully run through ArcGIS Enterprise Application Builder.
For demonstration purposes, the self-signed certificates that are included are sufficient, but if you like you can also generate a wildcard domain certs from the domain controller and bind this to the IIS root site that the web adapters are installed into. This happens after you run through the motions with Enterprise builder, and is a separate question.
Another approach for spinning up demo environments is to make use of the Cloud Builder for Azure/Amazon. This is my personal preference for quick deployments of ArcGIS Enterprise. You might even find your organisation has Azure credits, and I believe they also give out a free plan which might have enough credits for your demo purposes.
Suggest making friends with your IT team if required.