From Arlong Park's Manga SBS Page:
"SBS stands for Shitsumon o Boshuu suru, meaning, "I'm taking questions". Starting from Volume II, after the end of each chapter in the Tankobon Oda answers his fan mail. He takes on anything from intricately detailing the Marine Hierarchy, to some lighthearted things like explaining the measurement for how far Luffy can stretch with some... interesting units of measurement."

Oda's answers to his fan mail start off with mostly factual-type answers to questions and gradually develops into a humor corner which I've really enjoyed reading. Go check it out if you haven't already! (link above)

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Here's an example of one: (D = reader, O = Oda)

Chapter 167 (Page 26)

D: Hello, Ei-chan. I think I am in love with Miss Merry Christmas' way of abbreviating her "dammit, that's enough already!!" comments. Therefore, I would like to start this one like Miss MC would. "STUH!!" (Start the SBS!!)

O: WHAAAAAAAAAT?!!

D: Oda-sensei! Draw the six main characters with your left hand!

O: I don't want to waste any more space. Can I stop at three?

D: I've been wondering, how old are Vivi and Chopper? Vivi looks to be about the same age as the rest, but Chopper just seems like a kid! Please, give us the answer!

O: First, Vivi is 16. Chopper is a human reindeer, so as a human he would be 15. Yeah. That's right.

D: What would happen if I ordered "Fried rice! No rice!!" at a Chinese restaurant?!

O: Go try it and find out. Then order some boiled tofu without the tofu. Yeah!! What does this have to do with the SBS?

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Note, also from Arlong Park's Manga SBS Page: The translations for the SBS listed here were made by stephen. Please abide by his request and do not use them for scanlations.