Don't believe the story that pouring two cups of club soda directly in the center of a fire ant mound will eliminate the pests. The treatment is based on the idea that carbon dioxide (CO2) in the water is heavier than air and displaces the oxygen in the mound, suffocating the queen and other ants, supposedly killing the colony in two days.
“There isn't enough CO2 in two cups of carbonated water to suffocate an entire fire-ant mound,” says Linda Hooper-Bui, Louisiana State University entomologist. “The reason the mound may appear to be dead is you've poured two cups of water on them, and they moved because of the disturbance.”
The most effective way to treat fire ants is with baits that don't affect beneficial insects.