Work 2 jobs 8am-9pm M-Th, & I own P90X. What are fast, cheap foods to eat? Boiled eggs? Wheat bead? Help…?

I am pretty thin but my problem area is my abdominal area. Which you could never tell, but I can. I work all day in front of a computer and I want to know what can I bring to work that will build MUSCLE, loose body FAT, & have energy. I wish I could bring a blender and make protein shakes. What are my best options if I can only workout at 9:10pm when I get home, and what do I take after my workout.

My schedule is:
Monday-Thursday: 8:00am-9:00pm
Friday- 8:00am-4:30pm
Off Sat-Sun

Myself:
21
5’7
139lbs