The pilot reported that the airplane had not been flown in several months, and during the preflight inspection, he found that the brake fluid reservoir was empty. The pilot filled the reservoir and reported good braking during taxi for takeoff. At the destination airport, the pilot chose to perform a practice short field landing. The pilot stated that he immediately applied the brakes after touchdown but there was no braking action. He then vigorously pumped the brakes in an attempt to still make a short field landing. The pilot reported that the right brake suddenly functioned, but the left one did not. The airplane subsequently veered off the runway to the right as there was insufficient rudder effectiveness to straighten the airplane's tracking. The left wing impacted an airport perimeter fence damaging the wing and the lift strut. Additionally, the left main landing gear collapsed under the fuselage, and the right main landing gear splayed outward. The pilot stated that he could have easily made the midfield turnoff with no brakes.