Give me a procedure to be cheap in this situation?

I just started a diet. I work out every day, have for about a year, and I finally decided to start dieting as well. I’m not fat; I just want to maximize my workouts.

That being said, I am an extraordinarily cheap man. I have a box of boil-in-a-bag rice I bought from Kroger. Inside the box, there are 4 bags of rice. The directions say to submerge the bag and microwave it for 10 minutes. I think this can be accomplished with a Styrofoam cup for the water cooler, or the jar I use to hold my pens. That is all fine. The problem is, the bag of rice has 2 servings. I don’t want 2 servings, I want 1 serving. How can I make boil-in-a-bag rice with office supplies if I want to cook one serving? Can I store the cook rice? Below are my known assets. Help me be cheap people.

It should be noted, the box was $1.40.

Known assets:
Plastic bag I used for my sandwich. (Ziploc – Can I store the extra rice and heat it again tomorrow? If so, how?)
Styrofoam cup
Glass jar
Microwave
Also, normal office supplies

I want the left over rice for tomorrow!
Let’s go Jellies, I expect miracles.