Ptm Baker had already given his testimony to the Warren Commission but for some unknown reason the FBI had him come in, sit down and hand write another affidavit just before the Commission's works went into print. This document was entered as CE-3076.
In his testimony, the Coke machine was mentioned but there was no mention of Oswald drinking a beverage.
However in his first mention of the lunchroom encounter Baker stated that they [He and Truly] had made their way up to the third or forth floor before Oswald was encountered. That seems rather puzzling. By the time he testified though, he had learned to count to two.
"Mr. Belin - What happened?"
Mr. BAKER -" As I came out to the second floor there, Mr. Truly was ahead of me, and as I come out I was kind of scanning, you know, the rooms, and I caught a glimpse of this man walking away from this--I happened to see him through this window in this door. I don't know how come I saw him, but I had a glimpse of him coming down there."
http://mcadams.posc.mu.edu/russ/testimony/baker_m3.htmMr Baker had mentioned that Oswald was drinking a coke in earlier interviews. Apparently this could have been the reasoning for the last minute affidavit.
The words drinking a Coke are crossed out. I suppose it seemed a bit much to have to fit all that in after an alleged super dive from the sixth floor.