On October 22, 1994, about 1525 eastern daylight time, a Schweizer, SGS 1-34, registered to Tampa Bay Soaring Society, lost the brake and collided with a sign post on landing at the South Lakeland Airport, Mulberry, Florida, while on a 14 CFR Part 91 instructional flight. Visual meteorological conditions prevailed and no flight plan was filed. The aircraft received substantial damage and the commercial-rated pilot was not injured. The flight originated at Mulberry, Florida, on October 22, 1994, about 1505. The pilot stated the aircraft touched down about midfield during landing. About 200 feet from the end of the runway, while the glider was moving at a quick walking pace, he applied the brake, which had no effect. He directed the glider to an open area to the right of the runway and the glider struck a sign post and came to rest in a drainage ditch. He stated the brake cylinder developed a leak and lost all hydraulic fluid, and that he did not check the brake fluid before the flight.