TLDR: it’s candy

Heavy exercise causes your liver to flood your body with sugar so this makes sense.

As a diabetic it's a real pain in the ass. Light exercise lowers blood sugar but if you tip over into heavy exercise it shoots up. Can be a bugger to manage.

I much prefer fruit over candy for this.

A couple medjool dates usually does the trick. Those are pretty cheap, and about as convenient to grab and eat as candy since they're not messy and you can pack then easily.

Some other fruit that i really like for pre-workout are kiwis, pineapples, mangoes, and oranges. Those are all hydrating as well, which is nice, but they are a bit messier