Google quietly added a feature to the Google My Business spreadsheet uploads to enter URL attributes. These URL attributes can be used to link to things like your restaurants menu or other business information that is useful to searchers. Google posted this on the new features page and wrote "enter URL attributes for your business to add links to more kinds of information, like a restaurant's menu."
The help document explains:
URL attributes: URL attributes require a URL in your spreadsheet: your business’s online menu, for instance, appears at a particular web address. To edit a URL for a location, enter the URL in the corresponding attribute column.
So give this a try for your business listings.
Forum discussion at Google+.