Nothing reminds you of the daily grind you're supposed to be escaping from more than queuing with a trolley in supermarkets - and they don't change much from one country to the next.
But unless you're lucky enough to be staying in a hotel, you're going to have to go food shopping at some point...
Stock your fridge up on the first day so you don't have to go back.
Check out local produce
Buy fresh food from local markets, greengrocers or stores - you're more likely to find local produce there too.
When you do have to stock up on crisps and ice cream, go by bike rather than taking the car to make the supermarket run a (slightly) more pleasant outing.
As far as you can, avoid taking the car on small journeys.
You enjoy the environment far more on foot or on your bike and you'll avoid that other reminder of the daily grind, sitting in traffic jams.