You can use the bitset member to_ulong to make the conversion.
Code:
#include <iostream>
#include <string>
#include <vector>
#include <bitset>

using namespace std;

int main()
{
   string pizza("CHEESE");
   vector < bitset<8> > b;

   for (int i=0; i<pizza.length(); i++)
      b.push_back(pizza[i]);
        
   for (int i=0; i<b.size(); i++)
      cout << b[i] << endl;

   string pizza_name;
   for (int i=0; i<b.size(); i++)
   {
      char c = b[i].to_ulong();
      //cout << (int) c << endl;
      pizza_name = pizza_name + c;
   }
   cout << pizza_name << endl;

}