I am not sure if this works, but we received this from a Member:

An environmentally friendly cure for fire ants.

Simply pour two cups of CLUB SODA (carbonated water) directly in the
center of a fire ant mound. The carbon dioxide in the water is heavier
than air and displaces the oxygen which suffocates the queen and the
other ants. The whole colony will be dead within about two days.

Besides eliminating the ants, club soda leaves no poisonous residue,
does not contaminate the ground water, and does not indiscriminately
kill other insects. It is not harmful to your pets, soaks into the
ground. Each mound must be treated individually and a one liter bottle
of club soda will kill 2 to 3 mounds.

I so need to try this one.

Doesn't say whether they suffer, I'm kinda big on ensuring they do.

For those in North Texas, with temps hitting near single digits later this week it's great to stir a mound up real good as the temps drop - fireants don't like 12 degrees much.

That is interesting. For a double whammy you could use a sugar-sweetened drink...not diet.

Can't see how this wold work considering how extensive a ant hill can be...my guess is they move and then the mound comes inactive so the assumption is "it worked".

A box of grits is still the cheapest and works well.

I'd like to see someone experiment with both grits and molasses. My theory as to why grits might work is the nature of the fungi that decompose grits. That fungus might be detrimental or even poisonous to their food supply. Molasses works, I believe, by bringing a bacterium to the colony that would have a similar detrimental effect.