solar beer can heater...
https://duckduckgo.com/?q=solar+beer+can+heater&t=fpas&ia=web
...if you have apower source for the fan
Or, as dad used to say; “If we had some ham, we could have ham and eggs, if we had some eggs”
You can get fans that come with their own tiny solar panel. I see them a lot, usually lumped in with poultry supplies.