Peel the kiwis using this spoon technique and cut them into quarters. Toss the kiwi quarters in a large bowl with the sugar until coated. Cover and leave the bowl in the refrigerator for an hour, then come back and macerate the mixture, cover it again, and refrigerate it overnight. The next day the mixture should look like it is surrounded in a syrup and most of the sugar granules should be dissolved.

Strain the fruit pieces out through a mesh colander and keep the syrup. Some of the sugar will settle to the bottom of the syrup, and that is fine (once the syrup is mixed with the vinegar the acidic qualities of the vinegar will dissolve the sugar over a short period of time).

Add the vinegar to the syrup, pour into a sterilized jar, screw on the cap, and shake vigorously. Place it in the refrigerator and give it a good shake once a day for a week. You can let it sit like this for up to 4 weeks to allow the flavors to meld further. Once you're ready to use it, give it a final strain through a sheet of clean cheesecloth to remove any small seeds and pulp from the shrub.

Your shrub syrup is now ready to use! Feel free to mix it with water, sparkling beverages, juice, or cocktails. Make sure to keep your shrub syrup covered and refrigerated when not in use.