Basically, something free with the usual Subway purchases for regulars or anyone.
Subway's Subcard has a offer for new customers where if you sign up to Subcard via https://subcard.subway.co.uk/cardholder/home_uk.html,
iOS or Google Play Store, you get double points for the first 28 days (as long as you use the card concurrently a max 7 days after each purchase in the first 28 days, otherwise the account would revert to getting the normal points count). For every £1 you spend you get 20 points on your Subcard instead of the normal 10 points. The freebies points are below -
Free Hot Drink - 100 points (normally £10 total transactions)
Free Snack - 200 points (normally £20 total transactions)
Free 6in Sub, Flatbread or Salad - 500 points (normally £50 total transactions)
Free Footlong or 14'' Flatbread - 1000 points (normally £100 total transactions)
This means under the double points scheme for the first 28 days, if you spend £5 in one transaction or total transactions (a footlong sub) and scan the QR code on the app you get a Free Hot Drink, accumulate £10 total transactions and get a Free Snack (e.g. Nachos e.t.c.), £20 for a Free 6in Sub, Flatbread or Salad, and £50 for a Footlong or 14'' Flatbread. After the 28 days are up you can just spend the remaining points on the card, then make a new account to get double points again.
Also with Subcard you can get a free cookie on your birthday, and if you and your friends link each others account with Subsquad within Subcard, every time you or one of your friends purchases something from Subway, and the rest of your Subsquad make a purchase within 4 hours, you each get 50 points for each purchase to jump closer to the freebies (please don't post codes on here, against HUKD guidelines. I think only PM'ing is allowed).