What is the next letter in the sequence, Y, B, W, D, U, F?

S - It is based on every other combination of the letters of the alphabet coupled from the end and the beginning. Z,A and X,C, and V,E are omitted - T,G should be, so the next combo shown is S,H.

To keep awake driving late at night much earlier in life I learned to say the alphabet backwards in my head and then alternately like this from the ends in and the middle out, so I recognized this quickly.