A Cookup is what prisoners create out of various food items from the commissary list at their particular jail or prison. Also known as a jail-pizza, a Cookup usually consists of a mixture of squeeze cheese, pulverized doritos or any other spicy style chips, a pickle cut into tiny fragments, a sausage cut into tiny fragments and any other ingredients that would go well in the mixture like hot sauce. Everything is mixed into a paste and it laid over club-crackers, ritz crackers and even can be put between 2 slices of bread like a peanut butter sandwich. The paste can also be heated if the prisoners have access to a heat source. A Cookup is usually made by 2 or more prisoners, each adding their ingredients to the pot. A Cookup is a great way to waste time and serves as a special 4th meal, usually before lights out.

Another word for crack or cocaine

Comes from how you have to "cook" the herbs and other goods to obtain the delicious product.

So you "cook it up".