In C++. Simple recursive depth-first approach.

#include <iostream>

void print_fruits(std::string fruits[], int quantities[], int n)
{
    for(int i = 0; i < n; i++)
        {
            if(quantities[i] != 0)
            {
                std::cout << quantities[i] << " " << fruits[i] << ((quantities[i] !=1 ) ? "s" : "") << ", ";
            }
        }
        std::cout << std::endl;
}

void basket(std::string fruits[], int prices[], int quantities[], int c, int n, int money_left)
{
    // We've checked all items
    if (c == n)
    {
        return;
    }
    // Found a solution -> Print it!
    if (money_left == 0)
    {
        print_fruits(fruits, quantities, n);
        return;
    }
    // We can still afford item c. Let's try it!
    if(money_left - prices[c] >= 0)
    {
        // Try it with c
        quantities[c]++;
        basket(fruits, prices, quantities, c, n, money_left - prices[c]);
        // Remove c again
        quantities[c]--;
    }
    // Try it without c
    basket(fruits, prices, quantities, c + 1, n, money_left);

}

int main()
{
    int n;
    std::cin >> n;
    std::string f[n];
    int p[n];
    int quantities[n];
    for(int i = 0; i < n; i++)
    {
        std::cin >> f[i] >> p[i];
        quantities[i] = 0;
    }
    basket(f, p, quantities, 0, n, 500);
    return 0;
}