I think he is talking about when rumi was introduced. Pretty sure she was eating candy after she beat the other kids.
"Those drugs take the form of an everyday candy, fooling the consumer. It starts by inducing good dreams but slowly, depending on the person's mental fortitude, turns into nightmares. Eroding the said person's courage, ambition, or every other character trait helping a person marching forward..."
Katsuo managed to amplify his [Inventory Stomach] and its effect was that he could stretch his mouth to bigger proportions, meaning that he could put bigger stuff in it. It was gross before and now it was even grosser. Katsuo named it [Inventory Entrance Expansion], a rather "cute" name that didn't fit how gross the technique was in his opinion.