(covers information from several alternate timelines)
This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
Emergency rations, also known as ration cubes, ration packs, combat rations, field rations, or emergency ration packs, were food supplements typically used when food slots, replicators and/or conventional food supplies were unavailable. There were different types of ration packs. Some contained full meals with condiments while other rations were more in the shape of a cookie and were more geared towards providing needed nutrients than aesthetic considerations.
After Malcolm Reed and Trip Tucker's shuttlepod was damaged by a microsingularity in 2151, Reed found several ration packs that included veal marsala, Chilean sea bass, moo goo gai pan, and meatloaf with mashed potatoes. (ENT: "Shuttlepod One")
In 2154, Enterprise NX-01's galley was in disarray due to the damage sustained in the Battle of Azati Prime, forcing the crew to rely on ration packs. (ENT: "The Forgotten") After Trip Tucker repaired the galley, making it possible to cook proper food again, he planned to complain to the Quartermaster about their quality. (ENT: "Countdown")
In 2263 of the alternate reality, the USS Enterprise ejected several Kelvin pods after the Battle of Altamid when the Enterprise was critically damaged. Each pod was equipped with a survival kit that contained an emergency nutrition ration. (Star Trek Beyond)
Quantities of emergency rations were transferred to Deep Space 9 to keep it stocked until replicators and food supplies could be restored when the Federation took control of the station in 2369. (DS9: "Emissary")
When the USS Voyager was lost in the Delta Quadrant, the crew used rations to conserve power. One day in 2371, Kathryn Janeway had ration pack 5 while Chakotay had oatmeal from another pack. (VOY: "Phage")
Chief Miles O'Brien's many years of field duty gave him a certain appreciation for rations; he commented on them as being "the miracle of science" when he was one of the crewmen remaining during the Bajoran Alliance for Global Unity's siege of Deep Space 9 in 2370. He noted that field rations were one of the few things he missed about the Cardassian Wars. (DS9: "The Siege")
When Major Kira and Gul Dukat searched Dozaria for survivors of the Ravinok in 2372, they also had field rations. Dukat hadn't had some for a long time and assumed they hadn't become better since then; Kira then told him they had actually become a little worse. (DS9: "Indiscretion")
After their Danube-class runabout crashed on a planet in 2373, Quark and Odo had to survive on rations as the replicators were offline and the local plants were poisonous. Unfortunately, several of the ration packs were also lost in the crash. Quark would later say that the rations were "crumbs". (DS9: "The Ascent")
In early 2374, Benjamin Sisko and his crew were equipped with rations on a captured Jem'Hadar attack ship. After Nog told O'Brien they would have "plenty of field rations", something which even O'Brien thought would be a problem after eating them for three weeks. (DS9: "A Time to Stand")
The crew of the USS Voyager was forced to go to emergency rations in another alternate timeline after numerous Krenim attacks had damaged the power relays, taking the replicator system offline. (VOY: "Year of Hell")
In 3188, when Michael Burnham conducted a verbal checklist of her emergency supplies after surviving a crash landing on Hima, she confirmed that an emergency ration pack was in the kit. (DIS: "That Hope Is You, Part 1")