It was pretty common for neighbors to borrow foods that were under rationing during WWII in the small town where my grandparents lived. Especially stuff like sugar, coffee, cooking oils / shortening etc. I think it took some serious nerve to ask to borrow rationed meat, but the staple goods were often traded or borrowed and lent.
Even if one was careful, it was common to arrive at end of some foodstuff before getting to the end of the month, so then it was either do without or send one of the kids to the back fence to borrow it from a neighbor.
I was only past being a toddler but I do remember being sent to lend or receive borrowed kitchen items on a regular basis. "Don't spill it, dear" was the watchword... By the early 1950s I don't recall it being all that common to borrow staple goods in the suburb we lived in by then. We moved house a second time in that neighborhood in the late 50s. By then TV in the living rooms had already made families more insular, to the point we didn't even necessarily know each at all along the same block, much less well enough to ask to borrow some sugar or flour.
Funny how the men still would trade tools and other potentially expensive equipment, but once rationing was over I guess most women would have been embarrassed to run out of common pantry items.