Yes, it's for real, for the 'small' size sub(about 6" and $5).
Yes, you only need to buy a large drink and chips and present the coupon.
No, corporate does not reimburse their franchises for this, so some stores(but not most) have been refusing them. They make only about 8 cents on this with the coupon.
It was part of a promotion put out by citysearch.com, and they first had a july 31st expiration, then a july 10th expiration, then no coupon. Certain people have mirrored it, though, and it is still perfectly valid.
Check
here if you want any more details.
From my total lack of information other than forum posts and visits to the store, it's looking like a damn good promotion, maybe an order of magnitude less profit and an order of magnitude more customers, many of whom will keep coming after this is over.
