seek and you shall find

[BFG Central]

Train station,
Some long distant trains still have food on board.
If you acted quickly them fast food chains store masses of chicken and burgers, they also have concentrated soft drinks, coffee, tea, sugar, salt, pepper, ketchup etc.
People would be raiding shops and supermarkets first.
Chip shops for potatoes.
Factory canteens.
Commercial distribution hubs.
I have a massive refrigeration place down the road that stores thousands of tonnes of dairy products for all the major dairy manufactures.
So try and find out what companies are on your local industrial sites.