A fever is one of many symptoms that people view as a negative when it is actually a healthy response to infection. The common response is to fight the fever (which means the fighting the body) when what you really want is to support the body, which will alleviate the fever.
There is a really great protocol of foods, beverages, and more here:
Though this neglects to mention 1 crucial support directly which is that fever may be the body’s mechanism of recruiting calcium to fight the infection. So a calcium supplement may help reduce fever by alleviating the need to pull calcium out of the bones and other tissues.