I can confirm this. My wife used to work at a prison in California, and she told me about ramen being used as currency by the inmates. They would refer to ramen

I can confirm this. My wife used to work at a prison in California, and she told me about ramen being used as currency by the inmates. They would refer to ramen packets as "soups". It sounded like the inmates got just enough calories to survive, and often supplemented their diet by purchasing additional food with whatever money was given to them by family or was earned through jobs (which paid 10 cents an hour or something ridiculous like that). Ramen is cheap, has lots of calories, and lasts a long time, making it very popular. They also made their own alcoholic concoctions by storing fruit and various other things in their mouths and spitting it into a plastic bag, letting it ferment over time. That was referred to as "pruno". Pruno was considered contraband and would be confiscated upon discovery, so it was hidden in places like the toilet to prevent discovery. Pruno often turned out to be toxic in some manner, and sometimes made inmates very sick. It didn't stop them from making it though.