What can I give my yorkie for a fever?

What is your pups temperature? You should never give anything unless your vet tells you what and how much for your pup. Otherwise you are more likely to poison them and cause additional problems, even kill them. Medication is the number one cause of poisoning in our pets and more often given intentially by someone who means well but had no idea what they were doing than accidental ingestion. Just call your vet first and if it's okay they will give you instructions on what you might give and very importantly, the safest dosage for your pup.
You are more likely to cause more problems if you give anything without speaking to your vet first and also wouldn't have any idea if it's something you should be doing or would help your pup. What if you giving your pup something from home means that whatever medicine they actually needed can't be given if they can not be given together? You would have to have an idea of why your pup had a fever since your pup may need something else. If your pup is truly running a fever you should see your vet. You need to at least call and discuss it with them. It's always worth a phone call so you don't harm your pet further or even kill them by giving medication without a veterinarian's advice. 
http://www.petplace.com/dogs/over-the-counter-medicine-concerns-in-dogs/page1.aspx
http://vetmedicine.about.com/library/weekly/aa031502.htm
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/214039.htm&wo
q8911784.html#a3217554