Preheat your oven to 375°F (190°C). Lightly grease a 9-inch glass pie plate with a little butter and set it on a sturdy baking sheet for easier handling.
In a medium saucepan, combine the granulated sugar, water, and ground cinnamon. Stir well, then bring to a gentle boil over medium heat, stirring occasionally until the sugar is fully dissolved, 3–5 minutes.
Once the cinnamon-sugar mixture is boiling and clear, remove the pan from the heat and let it sit for 2–3 minutes to cool slightly. You want it hot, but not aggressively boiling when it hits the crackers.
Place the roughly broken buttery crackers into a large mixing bowl. You’re aiming for a mix of pieces about the size of a nickel, with some crumbs—don’t crush them into fine powder.
Slowly pour the warm cinnamon-sugar syrup over the crackers, gently folding with a spatula to coat every piece. Work carefully so you don’t completely mash the crackers; you want a soft, chunky mixture that will mimic tender apple slices.
Transfer the coated cracker mixture into the greased glass pie plate, spreading it into an even layer and lightly pressing it down so it fills the plate all the way to the edges.
Drizzle the melted butter evenly over the top of the cracker mixture. This helps the top brown nicely and adds that rich, bakery-style flavor.
Place the pie (still on the baking sheet) into the preheated oven. Bake for 22–28 minutes, or until the top is lightly browned and the edges are bubbling. The center will look soft but should no longer be watery.
Remove the pie from the oven and let it cool on the counter for at least 20–30 minutes before slicing. As it cools, the filling will thicken and set into a soft, apple-pie-like texture that slices more neatly.