This podcast might help: https://podcasts.apple.com/us/podcast/to-be-continuous/id1107185328?i=1000457501805
It can be very hard to track the ROI and the sponsorship can be more like a branding action than a direct sales one.
Other startups do it very well though. You need to track every company that visited your booth and make sure you will not give up on following them up until you get a no.