According to Official Guinness Records,
The most bicycles donated to charity in 24 hours is 5,512 and was achieved by Free Bikes 4 Kidz (USA) in Minneapolis, Minnesota, USA, on 10 October 2015.Free Bikes 4 Kidz has given away over 20,000 bikes over the last six years to people in need.
For a complete list of 2015 records, please visit 2015 Guinness Records in United States.