C172 Instructor Pilot reported wake turbulence from a military tanker overflying their aircraft resulted in an upset.

Narrative

Student and Instructor conducting an IFR cross-country training flight to IWA on an IFR flight plan. Requested the RNAV 30R IWA and subsequently cleared for the approach from Phoenix Approach. During the procedure inbound from WOGMA to WUMIX at roughly 3000~ MSL; IWA Tower instructed Tanker 'Heavy' to overfly us on the approach at 1000 ft. above. They then notified us that the tanker would be overflying and to be aware of its wake turbulence. The tanker overflew us by 1000~ ft. and was then cleared to descend; and that the Cessna behind was 1/2 mile back. They would begin their descent; and IWA Tower would notify us that he was descending and to be aware of wake turbulence. As quick as them saying that; our plane was thrown into a hard 60+ degree uncontrollable left turn followed by several uncontrollable seconds stuck in the wake of the tanker. The wake and the abruptness would knock our aircraft's G1000 AHRS system out momentarily until we were eventually able to level out and recover from the upset. The AHRS system would come back; and we would go on to land with no other issues and complete the flight.