The 26-year-old, who started his professional career with Central Coast Mariners before heading overseas to join PEC Zwolle and then Jiangsu, will be hoping for regular game time with Grasshopper as he attempts to impress new Socceroos coach Bert van Marwijk.
It is Sainsbury's second loan move away from Jiangsu after he joined Serie A giants Inter Milan last season, where he made one substitute appearance in Serie A.
The move should give Sainsbury the ideal chance to show van Marwijk his worth ahead of the 2018 FIFA World Cup.
We hope to work with him long-term," Grasshoppers' head of football Mathias Walther said.
"Trent is notable for his strong one-on-one action and his ability to build up the game (from defence)."
Last month, former Melbourne City striker Cahill signed with English Championship side Millwall while 20-year-old Gersbach moved from Norway on loan to French second-division club Racing Lens.
