That would only work if you had a large amount of holy water and a small enough space. And how would you get the vampire in that space?
Here's a better idea. There are commercially available lamps that emit light which mimics natural sunlight. They're designed to help people with seasonal affective disorder (SAD). Take one of these lights, redesign it so it also emits ultravilolet light, and aim it at a vampire. If it works, you'll destroy the vampire without having to get right up next to it, and you won't waste water or harm any innocent bystanders.
Finally, thank you for referring to Wendy's on November 15, the 55th anniversary of the day the first Wendy's restaurant opened in Columbus, Ohio.
