Language sneaks up on you
I refer you to Stan Carey’s excellent post at Sentence first on the word snuck, considered historically and linguistically.
And after you have read what Mr. Carey has to say, here are a couple of my own reflections.
I don’t like snuck myself and do not use it. To my ears it sounds not only casual but also uneducated. But that is simply a question of personal taste. As an editor, I wouldn’t dream of altering to sneaked in a direct quotation.* If it appeared in ordinary prose, I would have to gauge how formal the occasion was and who would be the audience before deciding whether to let it stand.
But this much is indisputable. The form has been steadily gaining ground in spoken English for more than a century. There are now many people for whom snuck sounds natural and sneaked artificial. Whether snucked will eventually become the dominant form of the past tense in written English as well, I can’t tell you. Probably no one else can with assurance. But it is not going away, and decisions about its use are purely judgments of taste and style rather than determinations of what is right or wrong grammatically. This is how language works.
*Actually, as an editor, I wouldn’t dream of rewording any direct quotation.