Mediates both low-affinity uptake and efflux of sugar across the plasma membrane. Forms homooligomers and heterooligomers with SWEET8 and SWEET17. Induced by the pathogenic bacteria P.syringae pv. tomato, and slightly induced by the powdery mildew fungus G.cichoracearum and the fungal pathogen B.cinerea. Belongs to the SWEET sugar transporter family. Truncated N-terminus.