Transparency seems to be a hairy topic, and I have used a lot of time to come to grips with it, trying quite a few experiments in the excellent Sketchfab factory. Here is my last attempt.
The model is one mesh.
It has an albedo/diffuse texture map and a png greyscale (stripes) map for the transparency slot.
However the transparency map seems to have no influence on transparency.
The transparency slider gives me even transparency on the whole object with or without the png map. If I use the same png in the emission slot, the greyscale has effect though.
I'm certainly missing something very basic here, that I could'n extract from otherwise really good tutorials (I thought there would be simpler solutions than the Coca Cola example).
I'd be happy to get some basic advice, as I'm new to this stuff.
Thanks in advance!