Read full details here: https://coinmarketcap.com/alexandria/article/what-are-fan-tokens
In conclusion, This coin main use is for supporting the team and not for an investment purposes. Same as buying merch online instead of using fiat, They introduced fan token to reduce transaction fee and also to introduce all the benefits for being a team fan on a single token.
so the value of this token depends on how strong the club is, and how many followers they have. so if you want to get a hold of this type of token, maybe, choose a football club that have strong social media presence as well as large number of supporters. and if you are a solid fan for that particular club, i believe you can optimise the use of this token by participating on their events or acquiring items related to the club.
the token itself is not backed by any known alt, but the value is determined on how strong the demand of the token is in the market.