The CandyFab heater consists of a resistive heating element that heats a metal tube. The first CandyFab heater was a modified soldering hot-air rework station. Following this was a version that used a ceramic heating element (a replacement heating element for a traditional soldering iron), with a copper tube wrapped around it.
More recent versions have used a stainless steel cartridge heater, either surrounded by a coiled copper tube, or potted (with furnace cement) in place with a stainless steel nozzle.
The challenging part of the heater design is to efficiently exchange heat between the heater element and the incoming (cold) air. Ideally, the heating element need not be maintained at a temperature much exceeding that of the melting point of sugar, approx 200 C.