@Rebecca10; it's simply annoying, I imagine the breast milk must be the most annoying thing. Sometimes I get guests that will eat a lot of food and replace none, others leave more stuff then they use. That gets equal over time. We learned over the years to have some staples in a locked space, to be able to cook something after arrival. It's ridiculous, but nevertheless a good thing to have some tomatoe sauce, fish cans, noodles, rice etc locked up, as you might have had guests who ate all the cans and the olive oil and you can prepare noodles with salt.
That's just the normal fluctuation, but we had one guest per year who was a nutcase and threw out everything. One year the fool of the year threw out all condiments from the fridge, another year's fool threw out all the content of the first aid box but for the scissors and emergency cover. One year a couple needed to empty the cupboard with rice, noodles and tea and the freezer. They handed me two big bags of stuff when I came back to explain the wifi. Thanks a lot! I put the staples into the garage box, but could only donate all the frozen food to neighbors, as I did not want to take it on a four hour train ride. They were vegan and felt their health threatened when my Italian pasta lurked in the cupboard. Although it contains only wheat and salt.
One thing you can do for the fridge: buy a large plastic box which you can close, label it "Private, do not remove" and put your stuff in there. I had put some stuff in open boxes, only to get the jam jars out easier at once, and this box was never touched.
I mention in my contract that the apartment contains private things in locked cupboards, on high shelves etc, which are not included and cannot be touched. That helps. Maybe include the box in the fridge.
