The Soviet students in Leningrad used to get food parcels sent by their parents who lived in the countryside.
I recall that we'd been warned to take vitamin tablets when we were in Moscow. Our Soviet pals in the hostel told us that during the Olympic Games, you could buy anything you wanted in Moscow. By the time we got there, October, 1980 you could get: sausage; bread; butter; sour cream; curds; chocolate; ice cream. Street vendors used to sell little sausage pastries. Once or twice, a wee hatch in a building would open and you could buy caviar on a bit toast...but I can't recall whether the caviar was Moscow or Leningrad.
Basically, the distribution infrastructure was rubbish. You could get eggs all the time in Leningrad, but not so often in Moscow. It was much easier to get good cheese in Leningrad too. Moscow had a chocolate factory, hence it was easy to buy that.
We'd treat ourselves to a meal in a hotel from time to time, but even then it wasn't "The menu, please..." Rather it was "Do you have meat?"
On my birthday in Leningrad I went to a restaurant. I was able to get a fried egg.
There was a long queue and a manager came out asking for someone who only needed a place for one...That was me.
To my consternation and embarrassment, I was shoehorned into a table with a family of Azeris from Baku. However, they were very welcoming.
I recall the dad insisted on pouring me a glass of blackcurrant juice from the jug they had ordered.
We discovered that the Pribaltiskaya Hotel on the outskirts of Leningrad had a Swedish Table where you could eat all you wanted for 2 roubles.
After that, we went there for a decent feed once a week...right until the tourist season started in June when my pal from Leeds Uni and I were stopped by an older doorman. We pretended only to be able to speak English, but he declared "You can't fool me!"
Apparently he thought that our western jeans etc meant that we were Russian prostitutes.