[{"cid":"PWER","data":[{"VALUE1":0}],"sid":"789069","units":"kWm","age":586667},
{"cid":"PWER","data":[{"VALUE2":809}],"sid":"788325","units":"kWm","age":11},
{"cid":"PWER_SUB","data":[{"VALUE3":278}],"sid":"789540","units":null,"age":1},
{"cid":"PWER_SUB","data":[{"VALUE4":319}],"sid":"789093","units":null,"age":38},
{"cid":"PWER_SUB","data":[{"VALUE5":0}],"sid":"789069","units":null,"age":4}

$ jq -r '.[] | select(.data[0].VALUE1) | .sid' data.json
789069

grep -oP '"sid":"d+"' file

awk '{if($0~/789069/){print $0}}' file

[{"cid":"PWER","data":[{"VALUE1":0}],"sid":"789069","units":"kWm","age":586667},
{"cid":"PWER_SUB","data":[{"VALUE5":0}],"sid":"789069","units":null,"age":4}

$ sed -rn '/VALUE1/ s/.*"sid":"([0-9]+)".*/1/p' VALUE
789069