 Heat stroke can impair a person's judgment, so they may not realize it's time to come inside. That's why experts urge everyone to keep an eye on colleagues, friends, and loved ones for signs of illness, which may include heavy sweating, cramps, tiredness, irritability, confusion, or nausea. Dr. Donna O'Shea with UnitedHealthcare says people should stay away from sports drinks and caffeinated sugary drinks and go for cold water instead.