Place the strawberries in a large glass dish (with a lid). Cut the vanilla bean pod into pieces and add it to the strawberries. Alternatively, add about 1 tbsp good quality vanilla bean paste or extract.
Sprinkle the sugar on top and mix it well with the strawberries.
Seal with the lid and refrigerate for about 2 days - allowing the fruit juices to be drawn out by the sugar.
Next, strain the fruit juices from the fruit chunks. There'll be undissolved sugar at the bottom of the dish (you will need this as well). To strain, transfer the fruit pieces on to a clean cheesecake cloth, and squeeze gently to release any extra juice stored in the fruits (do not squeeze out pulp). Add this juice back into the strawberry syrup in the dish and the settled sugar.
Add the apple cider vinegar to the strawberry syrup. Mix well until the sugar dissolves.
Strain through a very fine sieve into a sterilized glass bottle.
You could use it immediately, but the vinegar taste will be more pronounced then. Leave the shrub for a few days (about 3 days) to let the vinegar flavor slowly mellow down - it will continue to mellow down the longer you keep it, until it reaches a nice balance between sweet and sour (usually about 5 days). Give the bottle a shake everyday, to ensure the shrub is mixing well with the vinegar.
Mix the syrup with ice cold water or soda water or alcohol in a 1:2 ratio for a refreshing drink. Adjust to your preference. Enjoy!