Read it as a small scene about longing that goes unmet. Someone cuts into a cake that looks like a treat, but it has no sugar, and all that's left is a bitter aftertaste. The word "JUST" sits alone in capitals, and it stings: the cake offers nothing but bitterness, and the word makes that feel blunt and final.
The "she" in the second stanza craves sweetness, and the poem seems to mean more than food. Judging by the language, she wants affection or kindness, and "no one offers" it. Because she gets nothing real, she suffers, and the last line shows her "choking on aspartame," an artificial sweetener. The title, "ART?ificial," points the same way, with its question mark hinting at fakeness. What she's given looks sweet but isn't genuine, and it's hard to swallow.
The mood is bleak, lonely and quietly resentful. The short lines and sudden gaps make the poem feel clipped, like someone holding back how much it hurts.