Assuming he's macro cycling as well as IFing, are these low carb days?
I work in EMS and often have to eat on the run... but 20 minutes would still be a stretch to get in all his calories for one day. However, hard boiled eggs, nuts, and stews tend to be the best for quick meals. Eggs and nuts for obvious reasons, but I find stews are great because the meat falls apart in your mouth, making it easier to down large quantities in short periods of time. Just throw 4 pounds of stew beef, veggies, spices and a little broth in a slow cooker and he'll have food for a few days (at least.)
Hope this helps a bit, and good luck to my fellow shift worker!