Yes you can have more than 1 pizza box and cold pizza slice. As of right now, I have 5 pizza boxes, 4 cold pizza slices and 1 birthday cake. I rarely run out of energy but it can happen so I am debating about adding some extra on the side to be safe. Then again, its fully dependent on which missions you do for how much would be enough.
!ENGAGE 10
Thanks for the info!