I’m kinda surprised there’s room for it to happen on a submarine, but in pretty much any fort or other installation, there are lots of options to eat.
If you are off-duty, you can eat off-base, as long as you are willing to pay for it. But there are pay options on the base too. There’s always a canteen for the enlisted, and an officers’ club for the officers, and sometimes an all-base club which offers nice dining to all ranks.
Albeit, I understand that service at the canteens is being replaced by fast food options-- in some places, mall-style food courts. (Someone who has served more recently can correct me.) At any rate I think the workers in canteens have been mostly civilian since the 1980s or 90s.
Not sure how the nice restaurants are run-- they are not Grammercy Tavern or Daniel, but you could do worse for a wedding reception. They are more like a very good chain restaurant than a 4-star Michelin that would actually charge $500 for a meal in Manhattan, but I assume that with supply and demand at play after several weeks or months underwater, a Maggiano’s meal has more stars than the Milky Way. Albeit, I’m skeptical that a submarine has a Maggiano’s.
But, there isn’t a lot else to spend money on.
People on patrol of FTX get fed-- the military is good about providing food, but not necessarily tasty food. On FTX, on a base, someone in the kitchen packs up these thermo-tite containers called mermites (hot food hot, cold food cold), filled pallets for each company on FTX, and that was field chow. You didn’t get choices-- 1 fruit (canned fruit cocktail, usually), 1 veggie (frozen succotash, usually), 1 slice white bread, 1 kind of meat (usually some kind of dry patty), 1 8oz container white milk, 1 cookie.
If you were on patrol, or any kind of duty, you got an MRI thrown at you, and ate it cold.
Or, you got a buddy to bring you something better.
Smuggling food from the chow hall was not difficult-- buying better food and bringing it had to be repaid. Depending of where you were on duty, it did or did not pose the smuggler some risk. If a sergeant could catch your smuggler, and confine him to quarters for the rest of his off-duty time, he was going to want something; if it was a war situation, and not stateside, he was taking a real risk, so you might be paying some real money not to eat the MRI.
Is that realistic?
When you have guard duty solo, for a long time, and nothing to break it up, just having a buddy visit for a few minutes is something to look forward to. If he’s bring a hot meal of really good food, OMG, does it make that duty easier to take. When there’s not much else to spend money on, you might bribe someone a few hundred to bring you a $50 meal, sure.