ーThese rice crackers are supposed to be plum flavoured, but they don't taste like it.
「この煎餅は梅風味のはずなのに、梅の味はしない。」
They don't taste like 〇〇. で「〇〇の味はしない」と言えます。
ーThese cookies are supposed to taste like caramel, but they don't taste much like caramel at all.
「このクッキーはキャラメルの味がするはずなのに、全然キャラメルの味がしない。」
They don't taste much like 〇〇 at all. で「全然〇〇の味がしない」と言えます。
ご参考まで!