Mickey D's Coke secret … Fast food lovers have known for a long time that Coke tastes best at McDonald's ... but why? Shouldn't it taste the same everywhere? Well, according to Coca-Cola, it should taste the same, as long as every place follows Coca-Cola's guidelines to ensure the optimal taste and quality. McDonald's says they follow the guidelines word-for-word, and maybe other fast food restaurants do not. Per the guidelines, McDonald's says it cleans out its soda fountains with filtered water. They also use pre-chilled water and Coca-Cola syrup in their fountain – and make sure to use extra syrup so the taste isn't altered when ice is added to the drink. McDonald's says they also get their Coca-Cola syrup delivered in stainless steel tanks, which helps maintain freshness.