Let us briefly consider the chemical reaction of caffeine in the brain. And McDonald's action.

Caffeine is a central nervous system stimulant. It is structurally similar to adenosine, the chemical that is responsible for making you tired and regulating your sleep cycle. When caffeine is released into the central nervous system, it binds to the adenosine receptors and acts as an inhibitor.

By blocking the receptors, it counteracts the natural effects of the adenosine. In other words, the substance does not actually make users more energetic; it tricks their bodies into forgetting that they are tired.

Moderate amounts of caffeine are able to increase someone’s mental and physical stamina and make him more productive.  However, a tolerance is able to develop extremely quickly. In order to compensate for the adenosine receptors inhibited by the caffeine, your brain will create more receptors.

As a result of the increased adenosine picked up by your brain, you will begin to feel more fatigued than you would have had you never consumed any caffeine in the first place. Consequently, the amount of caffeine that would have once made you feel energetic is now necessary in order for your brain to function normally.

Caffeine withdrawal is characterized by headaches, fatigue, nausea and even depression in some cases.

Ok, so lets conclude that McDonald's intent to  giving us coffee for free is to make us more depressed, which leads to eating mostly, with fatigue that food will probably be easy and fast.

Truly scandalous Ronald McDonald..