He buys many boxes of different type cereal so he wouldn't get tired of just one kind. And, he buys instant milk. I know from experimenting and doing it in an emergency, that adding some powdered creamer to instant milk makes it thicker and taste like regular milk.
When buying instant milk, get the box with 1 qt. packages inside. If you buy a box with bulk instant and humidity get in the box it will turn into a brick, so get the boxes with packages inside. The cheapest price will be at Walmart as well as the cereal will be the cheapest there, too.
Now, think about how many types cereal there are. Look at those at the grocery and you see zillions of types. You wouldn't get bored with all those choices. They don't need refrigeration and will last a super long time. You will use a quart of instant milk before it needs refrigeration and/or you can make less than a quart at a time, just make the amount you will use for that meal.
If you have water, multiple boxed cereals, instant milk and powdered creamer, you can live a very long time.
For meat, I have canned meat. There is not a huge amount in a can so you will use it up before it needs refrigeration and that includes canned chicken. When I was into prepping years ago, I called the Hormel company. They said if the can seal isn't broken, the meat will last forever in the can.
At some time, after I started prepping, the govn. made companies put an expiration date on cans so the company was forced to put a date on. You will see a “best by” date which means the product will be at its ultimate best taste by that date but it does not mean the product is not good after that date. Due to what Hormel told me personally, their meat is good to eat regardless of the date put on there. Of course, if the can integrity is gone, like a crack in the can, do not eat it.