How to reference confidential data in reference list
Before you do anything with the confidential data, you should have cleared its use with the company in question. Giving away the data in any form without their express permission could get you into a lot of trouble.

That said, if the report containing the data is a internal company technical report, it should be cited as such in a bibliography. This provides enough information for a person to track it down, although you may want to state that it is not available to the general public.