When I was growing up, my father owned and operated a small wholesale grocery store in Eastern NC. His key customer base were the little country stores shattered around Eastern NC like daffodils in a spring lawn. While I can't remember exactly how many, but I believe at least a third served BBQ made in-house. My Dad told me that when these places bought vinegar by the gallon, that meant they were buying their BBQ sauce from others and diluting it down. Those that really made their own BBQ sauce bought it by the 5-gallon bucket. Scott's BBQ in Goldsboro, purchased vinegar in 55-gallon drums. (Scott's probably gets vinegar in a railroad tanker car now.) So, when I wanted a BBQ sandwich while delivering to these little country stores, I always waited until we got to place that purchased vinegar in 5-gallon buckets. My father always tried to buy as little of any product as he could get away with because he just wasn't a large volume wholesaler. The only things he ever got in large quantities were: flour, charcoal, salt, and tobacco twine. The flour because that was his private label. The flour was an ultra-premium mix and he had his own label, "Mother's Silk." Eventually, the minimum amount for a shipment of "Mother's Silk" flour increased to an entire railcar and he just didn't sell enough flour for that to work. The charcoal and salt were fall items. He sold them year around, but in the fall, just before "hog killing" he would order a railroad carload of each and be completely sold out by Christmas. Tobacco twine, balls and spindles, was a late spring/early summer purchase that he would send a truck to Wilson to pick-up. He'd keep a little bit of tobacco twine on hand year-round, but in the late spring and early summer, several trips were made to Wilson to pick-up a truck load of twine. The volume of my Dad's business probably doubled or tripled during the agricultural season. Some days during the height of the summer agricultural season, my Dad would have to rent a extra truck when his regular trucks filled up before all the orders that day had been loaded.
ETA: Forgot to mention, practically all these stores had gasoline pumps out front. But my father, in the strongest possible terms, told his employees and me to NEVER fill up the trucks at one of these little stores. Job 1 was to check the gas gage before leaving to make sure the tank was full. Job 2 was to fill the truck up at the end of the day to be sure it was ready to go the next day. My Dad had an arrangement with the highest volume gas station in town where he would be billed on a weekly basis for his trucks filling up on a daily basis.