After Sloane eats a little of his three scoop soda, we see the cup placed towards the middle of the counter where he is sitting. When he gets up to leave and the camera angle changes, the unfinished soda is now pushed to the far side of the counter.
When Martin is told it is only a dime for the soda, he puts his hand in his pocket, but in the next shot, he puts his hand in his pocket again.