Sorry to crash this as an American, but we have months of 45°C temperatures here in Texas with a really humid climate, so I might be able to offer some advice.

One summer my AC was out entirely for about a month. I survived by positively soaking a sleeveless tank in ice water and sitting around in that until it wasn't cooling me anymore and then soaking it again.

I recently found some ice packs that go around the neck, and they really work miracles for lowering one's body temperature. I always keep one in the freezer now for when I get back from a walk.

My mum always said to drink hot drinks in hot weather to regulate temperature. This was not her wisest advice.

My tried and tested technique of living in Shetland seems to be working.

Ice packs, the ones you put in picnic bags to keep the food cold.

I sit on one or put it in my lap during the day, and put another in bed with me at night. Great between the thighs for maximum cooling. Wrap it in a pillow case or towel or something so you don't have it directly against your skin when it's fully frozen.

1. Block sunlight coming in windows. Ideally with exterior blinds or reflective material on the glass. Interior blinds block light but not heat.

2. AC circulation. If your AC isn't hooked to your forced air than you'll want to circulate the air in your house to bring down the average.

3. Vent thorugh windows at night. Wait until it's below 20C and open at least 2 windows. Use a fan to force more airflow.

4. Hang out in the basement.

5. Upgrade your roof/windows. If you're from a warm climate your house probably isn't well insulated to keep heat in during winter; which also means that it doesn't keep heat out. Newer windows block UV light and have a higher R value which prevents heat from the air against the glass.

6. Plant climbing/creeping plants. They will absorb sunlight that would hit your house/etc and can create a micro climate several degrees cooler than the ambient temp.

7. Avoid wearing cotton and dark colours.

8. Wear a 360 large brim hat and sunscreen. Some of the "hot" sensation is actually UV damage.

If we weren't complete individualistic morons we would have district heating and even district cooling. You can produce chilled water with high grade waste heat with a absorber chillers. They use 1-3% as much electricity as the same capacity compressive cooler.

Paired with a soapstone sand battery you can sink over productive renewables (instead of shorting solar panels or stopping wind turbines) into high grade heat you can use later for winter heating or summer cooling.

Microfiber clothes soaked in ice chest and or dampened and frozen.

Wrap around your neck until it reaches ambient temp. Rinse and repeat (swapping out another one).

Hang out in the bathroom lol, not in Europe but if the AC goes out that's what I do. Not sure why but bathroom is always the coolest room naturally.

I have a hot bath every night, about 42-43 degrees c whatever the weather.

It sounds counterintuitive but a hot bath at the right time triggers your thermoregulatory system and you'll cool rapidly when you get out. It doesn't last long but I've noticed it.

Apart from that, a 2l frozen water bottle in front of a large fan at bedtime and blackout material on all the bedroom windows throughout the day.

Swamp Cooler.

https://www.itsoverflowing.com/diy-swamp-cooler/

Blowing on it really hard

Have you tried submerging your entire living space in mineral oil?