Dan crossed his eyes at the dark wave crashing on his face, opened his mouth, and let brown foamy liquid pour through. He thought “Chocolate malted beer?” and swallowed until the mug was upside down and empty. “How long does it take?” he asked, knowing that everyone else did too. “Not long” said a voice underneath him. It came from a middle-aged man doing one-handed push-ups on the kitchen floor. “Not long at all.”
Weird. Dan put the mug in the sink, dropped a fifty in the box at the end of the kitchen counter, and left.
He just made the 7:50 shuttle, running the last 30 yards or so. Hadn't done that in awhile, but he wasn't too winded from the effort.
Things went pretty well for the rest of the day. Dan eliminated

I'm confused. Aside from some structural stuff, too much has happened and it is heading in an erradict direction. First he drinks a beer, at least we think it is (that wasn't all that clear), leaves without saying bye. Runs to the train (you should have made it clear that's where he was heading), and then went to enjoy the rest of his day. Are you sure this isn't the entire story?
I can say that this doesn't hook me at all. Too much jumping around and I haven't the foggiest clue what it was about. I don't even have a clue what the genre is.
And that makes it difficult for me to suggest what should be done with it.

Good luck!

Structurally, the convention these days is to mark each speaker with a paragraph.

The voice isn't underneath him, unless he's standing on the guy, right? The voice might come from the floor. But did this guy just suddenly appear? How did Dan get into this place? Wouldn't he have seen the man? Some of these little elements are niggling at me. It makes me feel like the scene hasn't been well thought through, but the elements are being put in there for dramatic effect, at the cost of what's logical.

My conclusion is that he drank a liquid that's supposed to transform him somehow. Maybe give him physical abilities as hinted by the fact that he can sprint without much effect. I'm not really drawn in here. If I had a sense of why he was doing this I might be more interested, but I'm not that intrigued by the prospect of what might happen to him.