Sickness while exposed to sunlight is the hallmark of a developing bleed within the brain. The reasons for this are unclear. Usually there is a clotting problem and a hematology work-up and ptt is indicated as well as an MRA (not an MRI) This does not mean that this is the etiology (it is a worse-case scenario), however you have a problem that requires a timely evaluation by a neurologist.
Heat exhaustion rather than heat stroke will cause excessive sweating. This happens due to being overheated and sweating and so forth then you could get heat stroke after that. See my post above for what to do.
regards,
mkh9
she wouldn't have excessive sweating if she was dehydrated.
sounds like pre-syncope probably due to a sudden drop in blood pressure. which may be caused by slow thermoregulation.
did you notice if it happens only when standing up quickly? there's also something called orthostatic hypotension.
are you a smoker? if you are you should quit smoking.
I agree that it sounds like heat stroke and/or dehydration. You could be more sensitive than average to the direct sun or to heat, or, you may be having temperature regulation problems. (There are multiple possible causes for this, such as a thyroid problem.)
It also sounds like a vasovagal reaction, but I haven't heard of it being triggered by sun or heat before.
I would encourage you to see a doctor and get some blood tests before taking in extra anything.
It sounds like you are getting dehydrated and almost a heat stroke. Try to keep very hydrated and don't stay in the car long without AC. Bring water and a wet wash cloth to keep cool. You may want to get your blood electrolytes take (sodium , potassium, chloride and CO2) to see if you have a imbalance of these. You can also drink gatoraide and a banana to try to increase your potassium.
Sounds like your blood sugar is out of whack, your description fits to a tee. Check with doctor for diet change to stop this cycle.