Please provide as much context as you can with future questions, There are several things your words could mean, depending on the context. It probably means, "Allow us to pay for a coffee for you".
"Clarity trumps persuasion". (Website Name) is headed for clarity and focus. Please have coffee on us as we redesign and re-develop our website to ensure it meets your ...
So "Allow us to pay for a coffee for you" doesn't seem fit in this context. Is it?