According to Official Guinness Records,
The largest outdoor free floating soap bubble has a volume of 96.27 m³ (3,399.7 ft³) and was achieved by Gary Pearlman (USA) at Wade Oval Park, Cleveland, Ohio, USA, on 20 June 2015. Gary used two fishing poles with string tied between as the apparatus with which to make the bubble. An independent scientist calculated the volume through photography from orthogonal angles.
For a complete list of 2015 records, please visit 2015 Guinness Records in United States.