Homeopathy can help. My Mom can't sweat either, and she uses Glonoine (or Glonoinum) to help prevent or treat symptoms of sunstroke or heatstroke.
See also treatment.hpathy.com/homeo-medicine/homeopathy-sunstroke-heatstroke/
Also, a cool damp washcloth on the back of the neck or wrists can be helpful.
My Mom also uses a spray bottle full of water in the car for long drives in hot weather...she will spray her face, arms, neck as often as needed to provide external moisture to draw out heat from the body.
Chronic Lyme, Bart., Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut dysmotility & non-specific inflammation, Lupus, Osteoporosis, etc.; G-Tube; TPN-dependent
Meds: Flagyl, Zofran, Acupuncture, etc.