Why is coca cola zero so good/addictive?

I'm a long time coca cola drinker and I've always enjoyed a cold coke in a hot summer. But nowadays it's really gettin' out of hand in my opinion. Now there's a big difference between canned coca cola zero and bottled coca cola zero. I only drink canned because of that so called "first sip". Now that first sip is what is troubling me a little.

It's the sip I can't stop untill the carbon or coldness forces me to. Also, its only for coca cola zero. Not the normal one, so I did some more research and found out that zero is now with aspartam. Could this aspartam be something that's actually highly addictive? More or less like sugar, but just different?

I just wanna emphasize on that first sip, which is the reason EVERY SINGLE TIME i crack open a coca cola zero. Hell sometimes I forget/don't mind to drink the rest.

Its like hitting a crack pipe for that initial rush. Except it isn't crack💀