Citric acid which can be used for cleaning, cooking, or as a pH regulator. Food grade citric acid is a weak natural acid with potential descaling properties and a rust removing action. A very useful household product particularly due to its limescale removing properties.
 
Vegan friendly  and made from plants
 
Ideas for use: 
 
Descaling:  Dilute 1 or 2 tablespoons of citric acid in 1L of cold water and use this solution to descale coffee machines, kettles, cups, taps, showerheads and more Rinse with clear water afterwards. 
Remove limescale:  Remove limescale from your washing machine, put 6 to 8 tablespoons of acid in the drum and run on a cycle (90°C)
Toilet bowl cleaner:  Pour half the bag into your toilet and leave overnight. 
General household cleaning:  Replace vinegar as a cleaner throughout your home.