Ukraine

Here in Finland we have shelters on every bigger building, required by the law, and there should be enough room for everyone to be in a relatively safe space within few days if needed. In practise a lot of those are not in the shape they should be (full of stuff, without verifiably functional facilities for water/air/sewer/so on, but the hardware is there, it just lacks maintenance due to funding or whatever.

So, give us a week or two to get ready and after that there's a reasonably strong bunkers for every civilian to hide in for at least some time and if the society is still even remotely functional they can receive more food and resources. On the face value it's pretty simple. For every big enough apartment complex or any other building holding enough people you need to build a cellar or similar with necessary infrastructure and when the bomb shelter isn't needed you can fill them with storage units for residents and things like that. Everything inside just has to be built lightly enough that you can clear the space in pretty short notice.

As Ukraine will eventually rebuild a crapload of infrastructure and buildings something similar might not be a bad idea. And it doesn't cost Finland practically anything, we just need to share knowledge on how we did things and maybe how it could be improved. Maybe some Finnish construction companies could even make a few euros on building these things.

At least to me this is a no brainer, there's no losers on a deal like this. Civilian people are better protected in the end and it just requires sharing knowledge and experience, which doesn't really have any monetary value or political leverage. Maybe Ukraine can chip in with a bed, few warm meals and few cold beers for the experts on this field to travel and share their knowledge, but that's about it.