Bring a water bath in your stock pot to a boil. Prep your jars, rings and lids and keep warm. Meanwhile bring the 2 cups water and sugar to a boil in a small saucepan, whisking to dissolve the sugar. Remove from heat and set your simple syrup aside. Remove the canning jars from the water bath and fill with the cherries and two halves of vanilla bean in each jar, filling the jars about 3/4 full and pressing down a bit to compress the contents. Divide the simple syrup between the jars, filling each about 1/3 of the way full, then fill to the top with vodka, leaving 1/4" headroom in each jar. Place a lid and ring on each jar and finger tighten. Then place in the boiling water bath on a rack (make sure the jars are covered by at least an inch of water) and process for 9 minutes.Once the nine minutes are over, turn off the heat and let the jars sit in the water for five more minutes. Remove the jars from the water bath, set them on a dish towel to cool on the counter to room temperature. After they are cooled check to see that the lids are sealed. Dry the rings and screw them back on. Label the jars and store in a cool dark place for up to a year.