Sponsorships for football clubs are in the order of tens of millions per year, and usually there are big companies behind it. Bitcoin is not a company, there is no CEO, there is no shareholders, the only way would be that someone who actually owns thousand of bitcoins decides to simply sacrifice part of his fortune, but it's highly unlikely.
It is very rare, if we talk about promoting Bitcoin.
Some big exchanges like Binance seem to have done it, sponsoring soccer matches and Cristiano Ronaldo is also one of their ambassadors.
It's just like they want to introduce crypto at once including Bitcoin and those who see it are interested and trade on their platform.
But for people personally, maybe they just share Bitcoin information and explain it to the closest people or to their community.
Big events discussing Bitcoin and its development are also a place to introduce Bitcoin.
Like the Bitcoin Conference event that will be held in October in Amsterdam and this event is often done.
https://b.tc/conference