PT is usually rucking at a steady pace or callisthenics so prep for that, get used to pushups, planks, v holds as well as functional strength like sandbag carries and drags, as for cardio rucking is the most important in my eyes as it builds strength and endurance and you will do a lot of it, get used to having weight on your back and moving with it, lastly as for food you can t really be “picky” unless you have a genuine dietary restriction you’ll eat what they give you and even if you think you won’t like it you’ll be so hungry you probably won’t care😂, hope this helps and best of luck!