I am shocked that the Subway app allows this but it lets you to use the BOGO promo code (FL1299, 1299Ftl, FtL1299, FTL1299, BogoFTL depending on the month) along with the the every fourth sub free promo.

You get 4 subs

You pay for 3 subs at 50% each

Total paid = 1.5 subs

1.5

÷

4

0.375

1.5÷4=0.375

You’re paying 37.5% of the price of a sub per sandwich Or 62.5% off each sub