That's the difference between irony and sarcasm. Irony can be spontaneous, while sarcasm requires volition. You have to create sarcasm.
Christopher MooreChristmas crept into Pine Cove like a creeping Christmas thing: dragging garland, ribbon, and sleigh bells, oozing eggnog, reeking of pine, and threatening festive doom like a cold sore under the mistletoe.
Christopher Moore