Sperry has a few promo codes available that seem to stack. FRL-MT3-P6C-BGV has been around for a while and takes 20% off. MHG-DVK-K3F-QG9 is a new one I just found and seems to take 25% off.
This worked for me on desktop. I tried mobile but did not allow both codes to stack.
I bought the Roustabout, on sale for $110.99. It took the 20% off first knocking it down to $88.79, then applied the 25% which came to $66.59. (Odd that both came out to $22.20.)(Actually makes sense now...)
Use code FRL-MT3-P6C-BGV to take 20% off select items. Final sale for outlet items. Shipping is free. Once you apply to code to something in cart, then hit the back button you will see all of the shoes that the 20% will apply to.