How can I get rid of foot fungus without a prescription?

OTC antifungal. Creams, use powder to keep feet dry, wear sock that wick perspiration away from the skin. You have to stick with the program long enough for it to work. But if it isn't better within 2 weeks, see a professional and get a prescription.
Several ways. Good hygeine is first and then use a topical antifungal cream such as lamisil (terbinafine).