Not all plants have a use for the ones that for whatever reason don’t produce fruit. In the case of field corn, any stalk without an ear is prime for turning into corn syrup.
As field corn begins to develop ears it’s likely that you’ll notice a few that don’t. When that happens it’s time to make syrup.
Cut down the earless stalks at the base and give the wound a lick. Hopefully you taste a pleasant sweetness. That is the sugars destined for the ear that had nowhere else to go. Trim off the tassels and tear off the leaves.
Now there are two ways to go from here. The first is the low tech way- snip you corn stalks into smaller peices, throw them crush them well to access the juices. Then put in a pot and add water to cover and boil to extract the sugar. Boil the water down until it’s sweet then strain out the solids. Finish boiling into a syrup.
The more high tech way is to use a sugar cane press where you simply run the stalks through the press and the resulting liquid can be boiled down into syrup.
In both cases the sugar to water ratio is similar to making maple syrup. (What is that like 60:1 if I remember correctly.) Therefore you’ll need quite a few stalks to make a decent amount of syrup.