Make your own shakes. No need to buy expensive overpriced per made ones.
If you are using this as a meal I would make a MRP shake.
Grind up some oatmeal into a powder. I use a coffee grinder to do this.
Add that into our shake along with some natural peanut butter.
This should get you a good amount of good calories to keep you full between meals and give you energy for the physical aspect of fire school.