How can a friend class access the private members of another class?

[SomeAmazingGuy]

When a class has declared another class as a friend, how can that friend class access the private members of the other class?

I mean, I thought the function of the friend class have complete access to the private members of the other class.

#include <iostream>
using namespace std;

class Food
{
   friend class Drink
   string favoriteFood;

public:

   void changeFavorite ()
   {
    favoriteFood = "pizza";
   }


};


class Food;

class Drink
{
public:

  void useMembers ()
  {
  favoriteFood = "cheese";     //shouldn't this function have access to the private member favoriteFood?
  }



};

[keskiverto]

Yes, but of which food? Consider this usage:

Food apple;
Food beef;

Drink bar;
bar.useMembers(); // Whose favoriteFood? Of apple? Of beef? Of bar?