I made this weed killer spray in summer this year, applied it amply and didn’t have any issues with weeds anymore until now. It’s a simple mixture from household ingredients but indeed very effective and convenient. Mix in an ordinary spray bottle (though I, personally, prefer the pump type, like this):
500 ml water
500 ml plain household vinegar (the 5% acidity type)
6 tbsp. any salt
3 drops ordinary dish soap
Stir well until the salt has dissolved completely, then fill into your spray bottle. It works fine against weeds growing in the cracks between paving stones etc. It is not recommended to apply directly to the soil or on garden beds though.
Subsequently, just scrape off the remnants