Is ㄙㄨㄚˋ (sua4) for the character 嘴 from another Chinese dialect or language?

Question

In my explorations of my area of Taichung today I noticed this sign with Zhuyin Fuhao and took a photo to look it up when I got home:

And it seems that ㄙㄨㄚˋ (sua4) is not even an existing syllable in Mandarin, let alone a pronunciation of 嘴, which is pronounced "zui3".

Sometimes a Taiwanese (Hokkien, Minnan) pronunciation is used in some contexts here instead of the Mandarin one, but in this case it doesn't match the Taiwanese or even the Hakka or any other Chinese variety I can find.

Does anybody have a theory where this sound might originate?

Perhaps a Taiwanese word that people don't know the character for, and they just used it with this other character for some reason?

Answer 1

紲喙 (suà-tshuì)

合口味。
Palatable

形容東西合胃口、好吃，一口接一口，愈吃愈想吃。
The term describes that the food is so delicious that you want to eat more.

紲 is a substitute character (替代字) and means "continue".

source: 臺灣閩南語常用詞辭典

Answer 2

A similar question was also posted on Yahoo Answers. One of the answers read:

台語裡的~~~~"ㄙㄨㄚˋ嘴"?

正確的寫法是~~~~~"續ㄙㄨㄚˋ嘴ㄘVˇ"~~為求音準;借用英文字母裡的 " V "字的"音"參予拼音!

[續ㄙㄨㄚˋ嘴ㄘVˇ]的語意:就是吃了很合口味;意猶未盡;有欲罷不能的心情!也可以說成~~~~~"吃了還想再吃"! 台語裡的[續ㄙㄨㄚˋ攤ㄊㄨㄚ]的語意是:和好友"宴席"吃完;尚覺得意猶未盡;再換個場所繼續盡興!