Shorts-Sponsorship is described as the advertisment on an athlete's shorts. Handball and Beachvolleyball made shorts-sponsorship an interesting form of advertising for companies. It has not been very popular in soccer, altough the state associations of Germany have allowed shorts-sponsorship for their amateur teams.
Sponsoo has written an interesting Blog-Post about advertising on shorts (German): Geld verdienen mit voller Hose - der Siegeszug des Hosen-Sponsorings
Usually, Sponsoo does not act as a sponsor itself. But following an invitation from the Startup-Team "Startup United" , they acted as a shorts-sponsor for them.