Things I do:
1. Their water is in an insulated 5 gallon water cooler that I adapted with PVC and those chicken water cups.
2. I've been freezing 1-2 32 oz cups of water that I place in said water cooler every morning to keep the water cool.
3. Once I get the ice out of the cup my swirling it around, and thus ensuring all the water is cooled, I then take a cup of it and splash it into the water cups to flush out previous muck to clean it, and ensure water sitting in cups is cooled.
4. I've made up my own electrolyte mix for my birds consisting of equal parts sea salt, potassium chloride, and baking soda. I mix 1.5 tsp of this in a quart of water.
5. I will make some black soldier fly larvae popsicles using the electrolyte water and BSF that I pour into a plastic egg carton and freeze. You can also use ice trays.
6. I'll cut up a watermelon and leave generous red meat on the rind and give them some of those during the heat of the day.
7. I'll buy a bag of frozen blueberries and pour out a handful of these to thaw for a few minutes (if totally frozen they won't eat them), and will give them these as a treat.
8. I will hose down the dust bath with cool water, and I'll often spray down parts of the run. At some point before NEXT summer I'm thinking about installing some misters in part of the run and having a hanging planter system at the top of my chicken run that grows plants for extra shade and runs misters to water then and overspray down on the run to give the birds a cooling mist.
9. I currently have 2 fans running 24/7 during this horrendous heat. One blows the (hot) air in the run, and the other blows toward the coop to keep the air moving in the coop as well.
10. When I built my coop I designed the coop to be 2 1/2 feet off the ground w/ part of the run going under it for full shade (my birds practically live under there in the heat.) The coop roof is built with a THICK radiant barrier material that reflects a LOT of heat and makes the inside of the coop 10-15 degrees cooler than outside.
11. I have a shade cloth that covers the coop and the connected run. The support of the roof is tractor panels so it's an arch, that has hardware cloth attached over it (HW Cloth cage basically) with the shade cloth wrapped over that. So my coop is designed to offer as much shade/cooling as possible.