I am currently the Founder & CEO of Sweetberry, a healthy fast-casual chain. I am also the Founder of www.brandswaggin.com, a web development agency. I have experience in tech startups, ideation, web development, retail, CPG, finance, marketing, operations, and scaling companies. I have successfully franchised 2 of my own companies, and I have helped a dozen other companies Franchise as well.
If you are targeting runners, I'm sure that you have targeted actual races, where you can be a vendor and sell coffee to the spectators as well. To find running groups, try Facebook Groups, there are a ton of running groups in different towns. Also look up fitness/shoe stores as sometimes they put together running groups.