Working in the heat? I got you back.
This is not an advertisement.  I make no money from people coming to this page.
This is tried and hundredfold proven advice on what to do to fight overheating in real life work situations.

I’ve worked under the Texas sun for years now. Have developed literally a whole system of clothing, behavior, equipment to stay productive and NOT be dead at the end of the day. Think carrying a 25 ft ladder on all kinds of terrain, full tool belt on, working normally inches away from hot brick walls, A/C units blowing hot air up at me not uncommon, and so on.
Temperatures of 100F are common.
So is high humidity (exacerbates the problem).

Some of my work is in a different but no less hot and humid environment.  Vacant apartments, often without A/C.
That is another level of hell.  Partly because of the human smell/stench left after the tenants left.
But the same guidelines for heat protection, described below, apply.

First – the basics;

THE CLOTHES:
Shirts – nothing comes close to a brand called “Sport Tek”. Get the long sleeve kind. Keeps you the coolest possible.
(In winter  if you wear 2 a the same time it works in reverse – the two shirts keep you very warm.)
The fabric does not stain easily from oils and food. Actually it does not stain at all.
But paint, tints, etc. – of course.

It is best to have the Sport Tek shirt tightly fitting on your skin. Do not think that baggy is better – that is not how they are designed to work. Still work but tight fit really makes you feel cool and dry.

If the weather is humid Sport Tek will get soaked and not work very well. But compare to a cotton t-shirt – by that time you’d be dead – it gets 100% wet in the first 3 minutes and is like wearing a plastic bag.
Best is to carry a lot of Sport Tek shirts and change often.
They do not wrinkle. Folding them is impossible because of the sleek feeling fabric.

I’ve tried many “cooling” shirts – all of them overpriced to hell. None of them work. Sport Tek is the only one that does.
They come in all kinds of colors.
I personally love the neon green – makes me happy for some reason, not kidding.
Plus neon green identifies you as a worker.  In some areas that means you avoid a lot of trouble from the local population.

White is not better than the light colors.
But no matter long sleeves or not the Texas sun gives you a tan through the shirt.

NOW FOR EVERYTHING ELSE:

1. HAT.
Must have a hat. Breathable. White. Sombrero-like is best but soft so it does not bump on things and fall off your head all the time.

2. COMPRESSION SOCKS
Knee high compression socks. THAT IS A BIG ONE.
It basically helps your veins at the lowest part of your body. Meaning that your heart now has to move the blood in a shorter circuit – not really working all the way up from your feet. Compare wearing knee high compression socks to not wearing – the difference at the end of the day is HUGE.

3. LOW HEART RATE
NEVER get excited. Meaning no heart rate up and down. That is also huge.
Never get mad, never get too happy. Even keel.
Never get in a hurry. Makes a big difference.

4. HYDRATION
Gatorade can go back in its manufacturer’s ass. It is fucking worthless. Same with Powerade.
A dietician I know insists Gatorade works – for athletes that need fast, short bursts of energy.  But real life work is something completely different.
I’ve found and mixed the original Gatorade hydration mix – the one that some chemistry professor made for their Florida football team.
The solution is absolutely horrible to the taste because of the tons of Potassium content.
Hydration is about proper ratios of Mg, Ca and K.  Gatorade/Powerade are meant to taste good, not to hydrate you.

Same with straight drinking water – DO NOT try to hydrate with water alone. You can not drink enough. There are no electrolytes in it.
MUST have electrolytes the right way.
AND IN THE RIGHT RATIOS.

Best way to get a load of water in you – hold a Mexican Coca Cola (not the piss in a can) and a bottle of water. Sip from one then from the other. The sugar and acid in the Coke will stimulate your salivation and allow you to gulp both the Coke and all the water. Can’t do that with one or the other alone every 45 minutes. The sugar will give you a little high, the caffeine will give you a little high. The sugar helps the water to be absorbed. Try it and see.
No, it does not raise the heart rate.  I guess in extreme heat ingesting a small amount of caffeine is actually beneficial.

Best hydration drink – Coconut Water. But make sure it has no added sugar – most of them do. Must drink water along with it.
Also very, very good – Emergen-C – a powdered salt mix with lots of vit. C. Works like a champ. Different flavors. Well worth the money.
But it contains vitamins.  If you take too many packets it will cause elevated heart rate during the night.

But truly the best hydration drink is real yogurt diluted with lots of water.  Popular in the entire Middle East for centuries.
Not that great for the American palate.
Drinking it makes all signs of dehydration (leg cramps in the night etc) completely go away.
No need to drink too much – 4 tablespoons of yogurt a day in as much water as you care.

5. COOLING VEST
This is a military thing.
It’s a vest with thin plastic tubing running all over it like a net. It fits tight on your torso. A small pump circulates water. A backpack with ice and a little water is the source of super cold water. Need to change the ice every 30 min. Takes about 1 lb of ice every time for a 250 lbs man in 100F heat.

With that shit you can run like the Energizer bunny all day. BUT!
There is a huge  problem – your head is not cooled off. At night it will pulsate like a glow in the dark blob. They sell water cooled hoods, shorts, pants. You can go all out but I don’t think that is very practical.

6. COOL EARS
Keeping your ears cool goes a very, very long way. Best way to do that is to splash water every so often.
May end up with water in the ear because of throwing water at your ears standing up or half bent so be carefully.

7. LIGHT FOOD
Every single dumbass contractor knows that a big hamburger lunch with the shit French fries kills the productivity in the afternoon.
Eat very light but nutritious – meaning rice, clean protein, and some sugar.
NEVER a big meal.

8. OVERALL COMFORT
Anything that strains your motions or makes you move awkwardly and fucked up is overheating you without you realizing.
Blue jeans can go in their mother’s ass too – they were made for poor ass miners and cowboys. Not for contractors.
Jeans impede blood flow in the waist, groin, and knees. Can’t think of anything worse to wear in the heat unless you are riding a fucking horse in the prickly bushes in 1840.
But South American road workers, which are the backbone of road building in Texas, wear only blue jeans – partly because of safety regulations.
See if you too can do it. But do know – no matter what you do you can never be like those guys.
There are hard workers and then there are the road workers far beyond that. So keep that in mind.

9. NO UNDERWEAR
Most underwear impedes blood flow on your privates and groin. And/or it keeps the heat in the area that easily gets overheated.
Funny experiment – stick a hose blowing air in your pants and you will feel an immediate relief from the cooling effect – partly from evaporating all the sweat.
The opposite happens with jeans + underwear.
Baggy basketball shorts made of mesh material are the best.
But that is only if you work for yourself.  No company will let you work in such shorts.

10. BE AWARE OF BLOWING HOT AIR
Super easy to get overheated if you stand in the stream of hot air.
That could be air blowing from a fan or A/C or other equipment. Equivalent of drying yourself in a meat dryer.
The moving air feels good – then a few minutes later you can literally collapse.

Good luck.