On the subway app, from the date you set your birthday as when signing up, till 10 days afterwards each year, you will get a free cookie and a choice of either a free small cup drink, or a 430ml variety drink with the purchase of any sub, salad, or wrap.
this could be cheesed by just creating alternate accounts every day, but i havent tested it out.
Full fine print:
Available at participating Subway® restaurants only. Excludes delivery. Receive a free small cup drink or 420ml bottled variety drink and a cookie with the purchase of any sub, salad or wrap. Single use only. Products may vary by restaurant. May not be combined with any other offers, discounts or special deals. One offer per guest per transaction.
I didnt see this anywhere on the 3 pages of expired offers for subway, so i assume it hasnt been posted for whatever reason. its a pretty big one as well.