Why there is always around a horrible smell of sweat in Poland

That's what a bar of soap and deodorant prior to and afterwards are for while going out in public in the summer dude.
Sweat doesn't stink, three day old sweat stinks.
No excuse for pis poor hygienics besides just being lazy, having no self respect or pis poor parenting.
And it ain't just Poland with this low life mentality.

That's why you need to take a shower in the morning.

@Alien
Right now, morning AND night. It's been humid AF out here in Warsaw. If someone isn't bathing at all during this period, they're a straight-up terrorist and should be arrested.

At 35°C it is Ok.

Save water, shower with a friend.

Brits hate Yank tourists because Yanks use a month-worth of water in the first three days or sooner...

No they don't

I still remember from our vacations in England small sinks with two taps one with boiling water and one with cold water. You couldn't use much water....

You're supposed to put the rubber plug in the basin and mix the hot and cold water to your taste within the basin itself. They're still very popular in the UK especially with people into the retro/vintage style of decor.

And theoretically a building control requirement in a few towns in the north,

Nobody polices people installing the other kind, however in new homes in those areas you'll find two taps installed before the houses are signed off. These are usually in towns where most homes traditionally don't have hot water cylinders.

It's something to do with cross-contamination between hot and cold water