adding data in different date ranges

May need some work to make it more bulletproof but try this:

using System;
using System.Globalization;

class Program
{
   // ensure dates can always be parsed in d/M/yyyy format
   static CultureInfo ci = CultureInfo.CreateSpecificCulture("en-GB");

   static void Main()
   {
      string[] data = new string[3];
      data[0] = "5/5/2008 14/5/2008 40 40/10 = 4";
      data[1] = "12/5/2008 21/5/2008 30 30/10 = 3";
      data[2] = "20/5/2008 30/5/2008 55 55/11 = 5";
      DateTime start = DateTime.Parse("10/5/2008", ci);
      DateTime end = DateTime.Parse("25/5/2008", ci);
      GetFruitsEaten(data, start, end);
      Console.ReadLine();
   }

   static void GetFruitsEaten(string[] data, DateTime start, DateTime end)
   {
      string[] results = new string[(end - start).Days + 1];
      DateTime dt = start;
      for(int i = 0; i < results.Length; i++)
      {
         results[i] = dt.ToString("dd/MM/yyyy") + " = ";
         dt = dt.AddDays(1);
      }
      
      for(int i = 0; i < data.Length; i++)
      {
         string[] items = data[i].Split(' ');
         DateTime dt1 = DateTime.Parse(items[0], ci);
         if (dt1 > end) continue;
         DateTime dt2 = DateTime.Parse(items[1], ci);
         if (dt2 < start) continue;
         int eatenPerDay = int.Parse(items[items.Length - 1]);        
         int days = (dt2 - dt1).Days + 1;
         DateTime dt3 = dt1;

         for (int j = 0; j < days; j++)
         {
            if (dt3 < start)
            {
               dt3 = dt3.AddDays(1);
               continue;
            }
            if (dt3 > end) break;
            int index = (dt3 - start).Days;
            if (results[index].EndsWith("= "))
            {
               results[index] += eatenPerDay.ToString();
            }
            else
            {
               results[index] += " + " + eatenPerDay.ToString();
            }
            dt3 = dt3.AddDays(1);
         }                
        
       }
       
       foreach(string result in results)
       {
           Console.WriteLine(result);
       }
   }
}