I first learned about Survival Tabs prior to Y2K, but I didn't try them til years later. Evolved from the early space program in the 1960's, they come in two flavors - Vanilla/Malt and Chocolate. A full description can be found on their website, so I will skip that part for now.
These are some of the Chocolate ones. The manufacturer claims a ten year shelf life. The bottle above was packed five years ago. I opened it right before I took this photo. I don't know what "fresh" Survival Tabs taste like, but these tasted just fine. There was no hint of oldness or funkiness. I like the flavor of Survival Tabs. I can eat them like candy. They're sweet, but not sugary. The Malt ones taste a little like Whoppers without the chocolate coating. I like them as a snack.
It is also claimed that twelve tablets provide a full day's nutrition. I don't know about that, but they do help out a lot when there is not much food around. I haven't tried to go on Survival Tabs alone, but they make a great supplement.
I was reading the ingredients and noticed that they contain potassium iodide. Potassium iodide blocks the thyroid gland from absorbing radiation in the case of a nuclear emergency. I don't know if there is enough in these to get the job done, but it's something to think about.
The bottle is a bonus. It fits in a 1 quart USGI canteen carrier and functions as such. It was very easy to rinse out and had practically no aftertaste. The opening is wide enough to accept ice cubes. When filled up to the neck it holds a full 40 ounces. I was surprised. It doesn't look that big. If you choose not to re-use the bottle, it is made of recyclable #2 HDPE.
Survival Tabs are available at the link provided or on eBay. They go for about $32 a bottle. They can be had for $24 if bought in bulk. I have some, you should, too.