What is this promotioner giving out all year round?
Although I agree with you based on the size of the item in her palm that it looks like the size of a smartphone, it makes most sense to assume this is supposed to be a packet of white tissues (which should be drawn slightly smaller than it is in the close-up shots) because 1) tissues are the most common of such items to be handed out in public places throughout Japan, 2) many Japanese blatantly ignore and walk past the people giving out tissues without taking them, 3) they are often carried in a small plastic basket (though her basket visually looks like it might be wicker or some other material I've never seen one of these workers use in real life), and 4) they are given out year-round. I have on a couple of occasions seen clear files or lotion samples given out, and of course flyers without a take-home goodie, but I have never seen something on offer that looked like a white cell phone slightly larger than a packet of tissue.