Hi,
move the person out of the heat and cool him or her by whatever means available, for example:
put the person in a cool tub of water or a cool shower.
Spray with a garden hose.
Sponge with cool water.
Fan while misting with cool water.
Place ice packs or cool wet towels on the neck, armpits and groin.
Cover with cool damp sheets.
Let the person drink cool water or other nonalcoholic beverage without caffeine, if he or she is able.