Cut the rhubarb into short lengths and place them in a 16 oz glass jar.

In a medium saucepan, add the water, apple cider vinegar, salt, and granular sweetener and bring to a boil. Remove from the heat once the salt and sweetener has dissolved.

Pour the pickling liquid over the rhubarb.

Let cool, then seal the lid and store in the fridge for at least 48 hours. If you wanted to add the red food dye you can do this at any time.