Or, go really low tech and just use a clear tube for the PEZ and put black lines on it every 5 PEZ and let the user do a little counting.... LOL! But, where's the challenge in that?

Exactly! It was perhaps my very first idea and I thought "That's not over-engineered enough"

 

I originally did think of this too, but I decided I wanted to keep the external aesthetics mostly the same with just the display showing with the pez count.

Where is the Arduino going to hide?
It wouldn’t be hard to adapt force values over a slow spring change, considering the large change of a candy cycle, assuming you have access to a processor. Mounting the sensor in the head might lend to more options.

 

Ended up deciding that I want to be difficult and make a custom linear potentiometer because it's very compact so it's looking like it would be the least intrusive, but mostly I think it would be a good challenge that would force me to be better at soldering. I'll keep limiting myself from doing small scale hardware based projects if I don't take the time to practice. On Digi-Key I bought the CR0805-10W-102JT chip resistors and plan on placing them end on end. And yes, if you look into it, I got the minimum quantity of 5,000. If I mess up with the soldering I'll have spares, and it wouldn't be too hurtful on my wallet to mess up on a single resistor. I'll likely come up with something like a conductive wheel or a drag wire to place at the top of the spring to run along the resistor strip so I can pick up where the spring is.

Thanks to all who gave suggestions! I went into this with vague ideas that I wasn't sure about. Seeing some of you suggest ideas similar to what I was considering beforehand was reassuring and all the ideas have been tucked away for other potential projects. Appreciate the thoughts!

 

Where is the Arduino going to hide?
It wouldn’t be hard to adapt force values over a slow spring change, considering the large change of a candy cycle, assuming you have access to a processor. Mounting the sensor in the head might lend to more options.

The arduino can fit under the bottom of the spring. It's one of the big dispensers, not the normal ones that are a couple inches tall