with all the advice above. My experience has been largely on the ordering from and selecting caterers for sales meetings, conferences and executive briefings. Google your address and look for hi tech companies (Cisco, VMware, EMC.. , regional sales offices of real estate brokers, these companies/offices will typically hold weekly sales meetings for their teams and have monthly partner meetings for groups between 10 & 50. Many times, the receptionist at these offices will be the person who tells regional managers who is reliable and consistent which can be in my experience almost more important than food quality. I reused the same sandwich, chips, apple in a box sandwich shop at the same office in Los Angels because I lived 40 miles away and did not know the local area well for caterers. The were known & reliable so I continued to used them for over a year because the were reliable (it was Corner Bakery now that I think of it). If you do not have an issue with greasing the skids a bit... You may consider offering these key administrators & receptionists something you make very well at the appropriate time (not pizza for breakfast - not an omelet for lunch.) and let them know that you'd appreciate their help and that you'd make it worth their while when they com in. Another thing that works really well is to just deliver some food to "the break room or lunch room as no free food ever goes un-eaten in these types of offices. Some cleverly placed coupons (customized by you for that company by name specifically) to return let's say that week will let you measure your return on investment in the freebie and tell you which companies you are building loyalty with and where you should redouble or change to a new target.
Oh, also if you have any (there is probably a term for these types of facilities but I'll call them 'Executive Suites/Offices) Regus Offices this would be a good place to apply the above. In these cases the receptionist and meeting room is shared amongst all of the tenants. However, these are professionals who generally work in the field (read out of their cars) but need to have an office to meet clients, do training meetings, etc. if you get the handful of receptionists to recommend you it may have a multiplying effect across multiple businesses.
If you food is awesome and you make up packaged (lunch boxes, styrofoam clam boxes, etc.) don't forget to put a flyer or business card in the 'package.' In this case too you find that the people attending your customers meeting and eating your food are the local folks that are likely to want to come back to your business.
Have you done any collaborative marketing with other local vendors. Every business next to yours and down the street (storefronts) have staff. You could arrange a deal with a business who's product/service made sense (or no sense like say- a dry cleaner where you could offer to pay for all/part of their receipt tapes or clothing tickets if you could add your marketing/coupon to the back of these innocuous slips of paper) as it's it builds a bond with your neighbor. You know what I mean..maybe you have your tablecloths and whites cleaned professionally. Perhaps using a neighbor business pays a dividend you may not be getting for a uniform delivery outfit?
Depending on your local laws and license restrictions, I used to visit a number of offices and as my meetings were reoccurring weekly/monthly I would run into vendors with a big Igloo coolers selling either nuts, cookies, or organic free range boneless kelp stick in the lobby of or in the elevator foyer on each floor. If the building your targeting does not have a in building restaurant or snack shop and you can get the property management company's permission - this too is a good way to get to the people who need to eat at a place close by and you will reach some perhaps small but cult like following. It's critical that you show up at the same time and day every time like every Tuesday at 12:45 - you'll reach the people that don't have time to run out that day and get something and the people who had a weight-loss shake for lunch but would rather get a hot slice of your pepperoni for a fiver in place of a Snickers bar from the vending machine. Which reminds me of your soda vendor. Find out who the district manager is or which route driver has to restock the diet coke or Pepsi machines all the time. Where lots of sodas are being consumed - you have people eating at their desks, sales meetings, etc as suggested above.
You're far more brave than I. And I'd love to see you succeed! These are just the things that I would do if I were in your shoes. It may take some loss-leader upfront cost/loss but I think if done correctly you'll be able to measure where/who/when your seeing a return on the investment.
Lastly, if you are in a major metropolitan area you almost certainly have a local business journal. Every year they publish a "book of lists" which you can also get as a download for like $500 bucks or so. And it's free or available at a considerable discount if you subscribe to it - which you should because this will have all the local news of who's leasing new business space in the hi-rises and what hot new tech start up just got a trillion dollars from an angel investor, etc. all great opportunities to target the companies with lots of employees in your area and keep you ahead of others in your networking to build your brand.
PS: that store down the street. Hang out there when they are busy. If it's not the food and it's more pricey...there is a reason. Perhaps it's a very attractive cashier or a sandwich maker that over weighs the meats and cheeses. maybe they have a unique coffee that you can only get at that shop. You know what I mean... Keep your friend close - your enemy closer.
Best of luck!