Distilled Water and Seltzer Water
Water is not something think about hoarding, but since it is essential to life, you cannot live without it. Water is always the first thing on the shopping list for this reason. The first kind of water you should get is the purest kind: Distilled water. Store-bought distilled water will last indefinitely when properly stored. If left unopened, a bottle of distilled water can stay good for a couple of years.
You should also consider adding some seltzer water to your stash. Canned seltzer will add some fizz to your water and is excellent for relieving constipation. However, if you suffer from acid reflux, you should stay away from quinine and other carbonated beverages.