Bad service for me if not the same with one shop.

I bought iced coffee feom the Macdonald's in Plumstead and I was so disappointed because it tasted like water. I bought it first and it was the same so I decided to give them a second chance which didn't give me no joy. I ought one in Observatory that's when I got in love with their iced coffee but its totaly different and that's where my question lies because in my thinkung it should be the same as they must have the same receipe. It was very bad that I had to throw it away. Meaning my money went to a wrong place on that day.