This video shows you how to get two stickers: "Hot and Ready" for Quinn and "Preferential Treatment" for Whiff. It's a relatively simple process once you know how to do it! Definitely trying to 100% all the stickers in this game!
That one, and any other customer that has a special order sticker, you can just pull up that special, and make it when that specific customer comes in, and you can give it to them with no consequences