Since Carrefour, Lidl, and Aldi have moved into Spain you can get really good bread. Fresh milk is still a challenge. A couple of months ago after opening yet another fresh milk that had gone off we switched to Asturias uht which is very good. The Spanish don't generally use fresh milk for that reason I think.
I'm just back from a cruise. The bread was all baked on board as were all the cakes and pastries. The selection of fruit was amazing - I had the best strawberries I've had all year but they only appeared on the menu about a week into our cruise so I can only assume they were loaded at that port. Two days later it seemed to be apricots and oranges that dominated.
In the self service restaurant there were unlimited vegetables but the main dining room seemed to serve quite small portions of veg compared to the rest of the food on the plate.
St Petersburg cruise is great but it’s a full on busy one. So glad I did it though. Yes you see them loading up with loads of stuff in ports. They also sometimes do galley tours which is dead interesting as they tell you how many thousands of eggs etc they use during the trip.