Add the grenadine to the tonic water in a mixing glass, and mix well. Add the cherry cola and one shot of vodka at the same time. Place the 5 cherries in a seperate shot of vodka and soak for at least 10 minutes (cherries can be soaked in advance and kept in the refrigerator). Remove cherries and add this shot of vodka to the mixing glass. Stir, strain into a collins glass, and serve. Garnish with some more cherries, and serve.
More info on how to make a Pesticidal Cherries