Last night my wife and I had some tense moments when I told her I couldn't make an exception to pick up milk on the way home. I tried to explain where I was coming from: 'I'm not buying anything for a full week. If I make an exception, then I haven't succeeded'. Also, I had texted her to pick up milk, which I thought was sufficient. She tried to explain where she was coming from: 'This is all news to me.'
So, I guess my advice would be - when planning a 'No Spend Week' - be clearer during the preparatory phase about the specifics with the person with whom you share a milk supply. It will make both your lives easier.
Not to worry, she and I are back on the same page after a long chat. Also I traded a lemon and three Cookies & Cream flavoured drinking straws for a cup of milk from a friend in our building, and later bartered one of my stash of tallboys for a liter of milk from my sister.
We do still have 4 days of No Spend Week left, so if you have milk you want to trade for something I've got in my kitchen, please make me an offer.