I had this idea to make a kefir drink that was also a flu remedy recently. The culturing process makes the elderberry syrup even more potent and all the good stuff in the coconut water even better. Get the syrup version that is as unadulterated as possible, sans alcohol. The unsweetened tincture generally contains citric acid and glycerin, but it's still pretty clean.
3 cups coconut water, warmed to room temperature
4-6 tsp elderberry tincture
1 package of kefir starter
Mix the coconut water with the tincture. Thoroughly mix the starter and pour into a jar. Screw on the top lightly and leave at room temperature overnight to 24 hours. Chill and drink.
My daughter couldn't get enough of it...but do remember that 1 or 2 teaspoons of elderberry tincture is what you're supposed to take 2 to 4 times per day, depending on how proactive you're being. So that's maybe a cup at most!