How do you know your dog has a fever? What is its temperature? How old is the dog? How much water does s/he drink? Has he/she gotten into anything?
I was a veterinary technician for 6 years. If you are certain your dog has a fever, then I wouldn't recommend a home remedy (and note that I make herbal tinctures for own use). There are some underlying issues that could give your dog a fever. I would highly recommend taking your dog to the vet so they can give you an idea of the root cause. If your pooch does indeed have a fever, they may want to keep him/her overnight and possibly with fluids.
Is the dog dehydrated at all? You can tell by gently pulling up on the skin at the shoulders (just at the nape of the neck, technically). If the skin takes a little time to go back down, the dog's dehydrated. If it goes right back into place, then there's no dehydration.