Render Custom fields in email

[Kuubs]

Hello,

I have an issue that I want to resolve. I want to check every product it's custom fields so I can check whether or not a specific value is chosen.

But all I have in the product list are the numbers in the product_attribute field in the items array. I know these numbers correspondend to the values in the database. How can I render these fields to their respective values?

I know RenderCustomFields function exists in the customfield.php file in the sublayouts. But how do I use that in the email.php invoice override?