I used to take the subway to work, and usually walked past a grocery store or two - one downtown, and one a block from my apartment.

Because the overhead of shopping was lower (it was at most thirty seconds out of the way, on foot), I’d stop in a couple times a week, and picked up a bag or two of groceries that I’d just carry home by hand. It made it easier to be spontaneous.

For bigger trips, you could use a cargo bike or panniers. But I rarely felt the need. Buying in bulk was much less convenient than just buying an amount I could carry by hand, because it requires a special, deliberate trip.