Forgot to add well brewed coffee from a great local roasted bean source prepared by someone who knows what they’re doing. Perhaps a proper pot of tea made with loose leaves (not bags) again made by a worker trained properly to do it right.  
Finally Freshly made fruit juices. Many times well made Fresh Beverages can enhance the reputation of even the most basic establishment. Yet food and drink is only as good as the staff who prepare it.
Therefore as a owner and manger you must hire and train your staff with the utmost care improving skill sets daily. Finally consistency and Serve Safe regulations must strictly followed both in train and practice. The last point is what I find is the weakest link in independent operations. This is not meant to lecture but a observation of many years if dining.