Sounds like the can has been moved at some point during the animation, perhaps you moved once or similar. To repair the cans animation now, I would use the dope sheet and delete all the keyframes for the can of coke, make sure the first keyframe has the can on the table, then delete all the others and then copy the first key frame to the last keyframe position.

Then your can should stay in place throughout the sequence. To animate it scrub the animation to the point you want to have the actor move it, once the actors hands are holding it you can parent it to the actors hand and then the can should just follow the hand...

This is guesswork from a another noob, but its what I would do, perhaps some of the more experienced animators could comment too?