What would a group that gets cheap and or throwaway groceries and feeds homeless do in a Fit-Hits-The-Shan or End-of-World scenario?
You’d have to hope some heavily agricultural minded types would be friendly to you and your labor potential.
If there are functional societies elsewhere in the world, then help in the form of food could be on its way. The question is, will it be distributed efficiently to the people who need it? Something like Food Not Bombs could respond quite effectively to such a situation.
Primarily volunteering with them creates two things that are basically the most important things in any emergency:
1. Knowledge of who to talk to and where to go when shit hits the fan
2. Established practices of organization
If community resources are scarce, and you have a FNB cohort in the community, you have a group of people with lots of practice stretching out food, preparing it, and redistributing it to many people. Again I recommend solnit, she wrote about this exact thing happening in one of SF's earliest devastating earthquakes.
The other upside is when the State turns up to fuck your community efforts up (like they did in SF, or Louisiana after Katrina) you also have a group with established methods of peaceful resistance. They probably already have clout with the local State enforcement group: the SFPD have gotten to the point where it's basically impossible to get them to harass FNB because of years of softening individual officers to the cause.
Edit: I see now you mean, practically speaking, what actions could they take.
Well in a place like NYC I have no idea. Probably there would be huge issues with famine. Realistically the first thing everyone should do is get the fuck out of that city lmao.
I don't know if SF would be so bad. There's also groups like Food Not Lawns trying to get people into growing their own food. If their efforts continue to be successful we can have closer to home food supply chains. As for convincing people to share, for some reason that isn't all that hard. When capitalism and its disincentives fall away, it seems people revert to our basic evolutionary advantage of social bonding and organization.
Not to mention all the dry goods stashed in stores throughout the city can be stretched pretty far by the people who have practice at it. If FNB minded folks can redistribute from the stores quickly enough they might even be able to get to the meat and etc to turn into jerky etc - hopefully they'd abandon veganism in an actual emergency. Knowing them, probably not lol. But if I'm there that's what I'm doing.
Others have written on the plight of cities in anarchy, and I don't think it's quite so doom and gloom. "Conquest of Bread" was the OG and I think it still holds up.
But the locations were primarily Boston and San Francisco.