that 'japan' part written as ”じゃパン” from the sentence "じゃパンとポテトチップス".
it written using "jya" in hiragana dan "pan" in katakana, which i think means to emphasize the "pan" part.
looking at previous chapter MC made potato chips (ポテトチップス) and bread (パン or "pan" in Japanese).
so, i read it as a bread, sold under the brand of ”じゃパン”, hence "japan".