If APPLES is written as BORJHP, then how shall BANANA be written as?

Let's trace the pattern between the letters of the word APPLES and its coded version BORJHP:
* $\text{A}\stackrel{+1}{\to }\text{B}$
* $\text{P}\stackrel{-1}{\to }\text{O}$
* $\text{P}\stackrel{+2}{\to }\text{R}$
* $\text{L}\stackrel{-2}{\to }\text{J}$
* $\text{E}\stackrel{+3}{\to }\text{H}$
* $\text{S}\stackrel{-3}{\to }\text{P}$

The shifting pattern is alternating addition and subtraction with increasing integers: $+1,-1,+2,-2,+3,-3$.

Applying this same logic to the word BANANA:

* $\text{B}\stackrel{+1}{\to }\text{C}$
* $\text{A}\stackrel{-1}{\to }\text{Z}$
* $\text{N}\stackrel{+2}{\to }\text{P}$
* $\text{A}\stackrel{-2}{\to }\text{Y}$
* $\text{N}\stackrel{+3}{\to }\text{Q}$
* $\text{A}\stackrel{-3}{\to }\text{X}$

Thus, BANANA is encoded as CZPYQX.