Iodized salt. If there ever was a period of extended supply chain disruption this would be something that would be nearly impossible to obtain. It's something that's cheap and basically never expires. Salt is used in just about everything but the main importance is in food preservation. Iodine is also an essential nutrient, and iodine deficiency can lead to hypothyroidism and goiter. Iodized salt provides more than an adequate supply of nutritional iodide.
Second one the list is anhydrous caffeine. Anhydrous caffeine is an ingredient you often find in pre-workout formulations and is a dehydrated form of caffeine. It takes up much less weight and space than something like instant coffee, doesn't require any preparation and has a far longer shelf life. You can buy this in bulk, for around 500 grams (equivalent to nearly 5555 cups of coffee) in powder form for around $40 to $60 USD. It is a shelf stable product and as long as it's stored in a cool and dry place with little moisture it would probably last a long time, upwards of 10 years. This is something you could also probably vacuum seal. Add in some silica packet oxygen absorbers and I imagine you could store it indefinitely.
Also you can buy a 25 kilogram bucket, or 263,158 cups of coffee equivalent.
Third is honey. I have no idea how it hasn't been mentioned in this thread already but honey also has a near indefinite shelf life and a high caloric value. It's nutritionally dense, contains antioxidants and can be used as a substitute for sugar. It can be somewhat expensive to buy but if you are anticipating a SHFT-EOTWAWKI event this is something you want to have on hand.
Fourth is ascorbic acid (Vitamin C), Methylcobalamin (Vitamin B-12), Thiamine hydrochloride (Vitamin B1), and niacinmide (Vitamin B3) in dry powder form. These are four essential vitamins that you cannot live without. Even if you had your caloric needs covered, it's still likely you would end up with nutritional deficinies in these four areas. Without access to fresh vegetables or fruits your diet would be severely lacking in Vitamin C, which leads to Vitamin C deficiency, or scurvy. Scurvy ultimately kills you and it's one of the worst ways to go. Humans cannot synthesize Vitamin C, Vitamin B1, B3, or B12 by themselves. B12 deficiency is often overlooked, and even without the supply chain collapsing or some apocalyptic event, upwards of 20% of Americans have a minor B12 deficiency. Insufficient intake of B12 over a long enough period of time will lead to B12 anemia and a progressive weakening of the nervous system. B12 is found in animal products like meat and eggs, and assuming all you have access to is shelf stable food than this might not be possible.
Thiamine deficiency leads to a condition called Beriberi and leads to serious impact on the cardiovascular and nervous system. Niacin deficiency leads to pellagra,
The reason I recommend these on their own instead of something like a multivitamin is that multivitamins will not have the same stability.
Proper storage for dry vitamin powders should be mylar bags + oxygen absorbers or vaccum seal + oxygen absorbers, stored in something like a Leaktite bucket with a gasket.
In most of the world, food is required to be fortified with certain essential vitamins and minerals to help prevent widespread nutrient deficiencies in the population. This is why people aren't walking around with beriberi or goiter. In America certain foods are actually required to be enriched with certain nutrients for example refined grains like bread and pasta are required to have iron and B-vitamins. If this wasn't the case, the average American diet would not have adequate intake. People had a lot of horrible fucked up diseases before modern nutritional and dietary standards came into being. Even if you were able to completely get your own food supply up and running, it would still be difficult to match the current modern industrial standards of nutrition. This is why if you are serious about long term food storage to get these things on their own. Autistic, yes, but completely overlooked.
Also as a quick sidenote. "mypatriotsupply" or whatever freeze-dried meal packages grift BS that's sold now fucking sucks. It is indeed
food and sustenance that would definitely get you through an emergency but the quality is so low and the price is so high it's much better to just buy stuff yourself. The macronutrient profile is also very poor, with little protein and fats, and most of the calorie content coming from pure carbohydrates. This is not what you want for long term food supply. From the sites I've looked at they are almost always fraudulent in their labeling, often saying that the "kits" they sell are for "30" or "60" days with "a million calories", and then half of that milion calories being like kool-aid powder or something. The only real advantage to freeze dried food over something like regular canned goods you can get from any supermarket is weight and space reduction. But this really shouldn't matter if your plan is just to put it in your pantry or in a 5 gallon leaktite bucket in your closet. Mountain House meals are good for camping though, it's really the only brand of "freeze dried meals" that are edible and have a good macronutrient profile, with a high amount of protein. The problem is they are incredibly expensive.