When we ran our barbecue trailer up in Illinois, our little dual-axle trailer looked like a little cabin, with a massive Rotisserie Barbecue pit and kitchen entrance in the back, and a serving window in the front. We had a few picnic tables set-up near a popular shopping complex and intersection. Business did not survive, but we learned a lot. One of the highly requested items after we began serving smoked brisket, ribs, and sides, were something called Lemon Shake-Ups. This was 2005, the recipe was pieced together with what we could find at the time on the internet, and a book we found.
Once we began serving these, in the summer months, sales did assist with the bottom line. Since then, over the years, on hot days, we would buy a bag of lemons from Sams, mix up some simple syrup, store in refrigerator, and serve them as needed over the weekends.
For best flavor, always use fresh lemons, squeezed over ice, simple syrup, and shaken vigorously.

