Invade Brazil, which should take only a couple of weeks, with no pushback by any other South American nations, I guess... And then what ? Put water bombs on the F18s ?
It's kind of fascinating the pavlovian answer is jumping straight to military invasion rather than something like "try to have the international community negotiate a deal with Brazil to fund / manage firefighting" or "forest preservation" or somesuch. Not a magical solution by any means, and probably means sweetening Bolsonaro with billions in grant -some of which will assuredly get grifted- but still less expensive, needlessly cruel & lethal and probably more efficient than a WAR.