Place the nectarines, rosemary, and honey in a large jar or seal-able container. Mash the nectarines and honey together using a muddler or wooden spoon. Cover with a lid. Place in the fridge and let sit for 2 days, shaking occasionally. After two days, pour the mixture into a fine mesh sieve, pressing on the solids to strain out the fruit syrup (alternatively, you can blend the whole mixture and then strain it through a sieve to get the most fruit and flavor out of it). Place the syrup back in a jar and stir in the apple cider vinegar. Place back in the fridge for another 3 days. Shake syrup before using.
Mix 1 part syrup to 3 parts sparkling water and pour over ice. You may like more or less syrup, depending on your preferences
Garnish glasses with nectarine slices and a sprig of rosemary.
Recipe by The Kitchen McCabe at https://www.thekitchenmccabe.com/2016/09/01/nectarine-rosemary-honey-shrub-fizz/