Seek the beverages associated with British Colonial Rule: Gin has juniper, which seems to have a cooling influence; maybe quinine is a sort of febrifuge, so you might want to splash a little tonic in that. It is hard to say what herbs may actually lower body temperature: Loss of blood might do it; any bodily fluid that can be released may conduct heat away from the body. Mints have a reputation, and may indeed have a role in the release of sweat. Some anti-inflammatories may have such a mechanism, releasing liquid from swollen tissues. I hate to tell people to consume herbal concoctions that are not generally available because individual chemistries, indications and advisories may vary over time and target population.