Do you mean Field Training? If so, it's more of an evaluation than a training event, which you attend through a competitive selection process after two years in the program. This allows officers from outside of your detachment to get eyes on you and confirm if you're ready to become a member of the POC (AFROTC upperclassmen). Google AFROTC field training manual and take some time looking through it- it has a generic schedule and a lot of other information.
There is currently no other mandatory AFROTC summer training but there are opportunities out there for high-speed cadets. There's Project GO, a ROTC-wide language and cultural development program; depending on funding, there are opportunities to shadow career fields like CROSHOW; there are internships and school programs available through Arnold Air Society/Silver Wings (and scholarships- AAS/SW is a good deal) with organizations like the Air Force Research Lab, the Air Force International Affairs Office, and the Air Force Association.
Aside: the summer safety net that allows you to make up courses so your academic plan isn't totally sunk is underrated. They can be expensive and it of course won't save a low term GPA, but the intensive environment can be just what a student needs to get that information to click where it previously wouldn't.