I pointed two small, but powerful fans at the run/coop during our extreme heat spell with a frozen bottle of water in front of the fans. It cooled the run and coop. I also used fine mist water from the hose and a bit of ice cold watermelon. For their two regular wate containers r I changed it several times per day and floated a block of ice in the open dish and a frozen bottle of water in the double wall fount. I use old water bottles and throw-away type of containers with lids that I freeze several to have on hand to use through-out each day.
Since I have a movable coop and run I moved everything under full shade of large trees but if you don't have any natural shade a tarp of shade cloth (or anything that will block the sun) will work wonders. The very hottest day I also sprayed the surrounding area, the tree tops, and the top of the coop and run with cold hose water as the evaporation of water cools down the surrounding area.
The birds really liked the fan and ice cold water the best - sticking their rumps into the fan breeze which blew their feathers the wrong way but lots of air to the body which released heat. It would end their open mouth breathing each time.
I gave them their regular layer feed during this time (and the watermelon) but nothing to spend energy (and generate extra heat) scratching around hunting for stuff. They continued to lay but the eggs were not as large. My birds are not heavy type birds nor are they too fat, plus being hybrids they are supposedly able to take heat and cold better than some of the true breeds, in particular heavies.
I noticed they also liked to stand in the cold water. Anything up to 95 they are OK with just shade and fan and didn't need ice water, but when it hits anything over that, and it went to 105 and up a few days, it did take the extra measures to cool them. Sometimes I also added Quik Chic to the water to replace electrolytes.