Mintel - Mintel is a good source for tangential content like "Digital Advertising" and "Sports Drinks" which feature sections on Celebrity Endorsements and Consumer Demographics.
Statista – Under the "Consumer Insights" heading, you can find surveys on topics such as "attitudes towards sports," "sporting good purchases," and "professional sports follower."
RKMA – RKMA’s report on Sports Marketing includes a demographic profile of sports fans as well as ticket sales, attendance, viewership, etc. of major sporting events (based on US data).
Sports associations or leagues often have their own reports on attendance, ticket sales, or viewership that’s publicly available. Use Google or news sources to find this information.
