Mishnayos Yoma Perek 8 Mishnah 3

If one ate and drank unwittingly within one lapse of awareness, e.g., he forgot that it is Yom Kippur, he is liable to bring only one sin-offering. However, if he ate and performed labor unwittingly, he is liable to bring two sin-offerings, as by doing so he violated two separate prohibitions. If he ate foods that are not fit for eating, or drank liquids that are not fit for drinking, or drank fish brine or the briny liquid in which fish are pickled, he is exempt, as that is not the typical manner of eating or drinking.

אָכַל וְשָׁתָה בְּהֶעְלֵם אַחַת, אֵינוֹ חַיָּב אֶלָּא חַטָּאת אֶחָת. אָכַל וְעָשָׂה מְלָאכָה, חַיָּב שְׁתֵּי חַטָּאוֹת. אָכַל אֳכָלִין שֶׁאֵינָן רְאוּיִין לַאֲכִילָה, וְשָׁתָה מַשְׁקִין שֶׁאֵינָן רְאוּיִין לִשְׁתִיָּה, וְשָׁתָה צִיר אוֹ מֻרְיָס, פָּטוּר: