Same content for each sub-brand

I have a client who wants to start an online wine shop. For the sake of this post let’s call it Supreme Wines. He wants to white label it so that other companies can have their logo in place of Supreme Wines, whether it is at a different url or in a subfolder on the same website. Everything else will look the same, the content will be identical as my client wants to only update and change one website content – he is in control, the sub-brands won’t need to do any admin at all.

Let’s assume one of the other companies (sub-brands) using the website content is called Grapes.

My client wants to handle all sales and correspondence from sub-brands such as Grapes through the admin of the main site Supreme Wines. The sub-brands will not have access to the admin side.

There will be a register button and access for a customer to see previous orders so he can repeat purchase his favourite wines. My client (Supreme Wines) will need to know which customer has registered with what sub-brand.

How can I set it up so that my client (Supreme Wines) will know which sub-client (Grapes for example) has which customer so that he can distribute profits from each sale back to the right sub-client?