Meaning . . . what, exactly?

Corn syrup makes an item outdoor good. Which outdoor? The Golan Heights were outdoor. Babi Yar was ourdoors. The entirely of the battle of Gettysburg was conducted outdoors.
Well, this is ridiculous. It’s just a patently obvious attempt to double syrup consumption.

Just a guess, but: the phrase “pour-on” smacks of industry lingo. As in: well, the boys have run the numbers through the Univac, and pour-on sales are projected to go nix-wise in the next two quarters.