By living in a country with no seasons

Drink lots of water, I guess? An air cooler might also come in handy - they're way cheaper than an AC. And yes, don't hold your yellow pee, because the burn will be intolerable.

If no ac then stay in the basement while I reasonably can. Drive with windows open. If my work has no ac then the business closes. The material we work with has to be temperature controlled.

Buy a dual hose portable AC, that's what I did when I lived in an apartment that would get VERY hot no matter what. (Actually, to save some $$ I got a single hose and modified it to a dual hose, but depending on the specific model and the tolerances they built it to, it risks short cycling and possibly burn out)

They're still not nearly efficient as a window AC, but far far better than those single hose ones

If you can fit a window AC do that instead, if you are able to make modifications, a small mini split/heat pump system would do wonderfully. Though I have heard that they make mini splits that go through small windows rather then needing to drill through the wall, so that might be an option too.

The other tips and tricks are nice, if you have exhausted all other AC options and simply can't have an AC at all (Which is mostly due to cost, dual hose portable ACs are pricey) but they really don't compare to an actual AC system.

Get a dehumidifier.

Ensure ceiling fan rotation is switched on summer mode.

Bag of ice in the freezer to chew on and always have in a drink. Ice trays are no good.

Waterhole.

Office job.

Keeping lights off/low can be psychologically "cooler" for some.

Bed with wet hair or damp towel will help sleep faster.

Wash regularly to scrub "ick" layer and keep fresh skin on top.

Pub.

Ice pack vests. Can DIY. Fucking amazing.

Sit around in your undies and pretend you love it and eventually you do.

If you have a basement, stay in it. When it was 108°F here in Seattle the other year, it was in the mid to high 70s in my basement office. If you do not have a basement, am evaporative cooking method can cool you a bit of you are in a dry climate. You could also hit up a pool or grocery store or movie theater. All those will help you cool off.

Check Craigslist for a portable AC unit. I was able to snag a free dual hose portable AC unit a month ago. The hotter it is though, the higher the prices are on Craigslist.

Keep windows open at night and into the morning

Fan pointed straight at you, on max blast through the night

It's significantly worse if your house is humid, and dehumidifiers increase the heat, but they're still worth it

A cross breeze is great. I can often turn off the ac during a hot day and just open the windows.

Buy a portable AC unit and install it in your bedroom or living room window.

EDIT: I have this one that works well at least on a single room: https://www.amazon.com/Vremi-000-BTU-Portable-Conditioner/dp/B084H4B6NB?th=1

If you live in a dry climate you can create a makeshift evaporation cooler with a fan, tub, water pump, and evap material.

Set it up in front of an opened window, blow it into the house, and open a window at the other side of the house. You can easily get 20 degree F drop in temp.

Get a cold wet towel wrapped around your neck. Feels so good.

At my family cottage, we had it for over 40 years before getting portable ACs. Generally we just avoided the heat waves. Cold waterbottles in between your neck and shoulders really helps circulate the cooled blood throughout your body. We ended up getting portable ACs one year because we were spending a week there and it was over 95f every day. A few years later one of us took a paid early retirement package and we used some of that money to get central AC, best upgrade for our cottage ever.

You dont wanna just be blowing around the oven-like air trapped in your house. Open two windows on opposite ends of the house, and point a fan facing outside at one of the windows. This will pull air from the opposite window and create a crossbreeze of fresh air.

Lying shirtless on a hard floor can also help cool your body down

Happy cake day!

Do you have ceiling fans? I honestly have rarely even wanted AC because ceiling fans do such a good job at keeping the place cool up to at least the low 30s, when I'm not headed up from doing exercise.

Never take a hot shower. In fact turn off your water heater if you can. The goal is to avoid having hot water in your pipes heating the house

Go for a drive, I have AC in my car...