The subject is not undebated in the scientific community, true. However, if you google for scientific papers on the subject, you will realise that the studies observing behavioural patterns that can be classified as addiction under the most popular definitions (since there isn't really a unified definition of addiction) are quite numerous, while you'll find only a few arguing the contrary. And their argument is not that it doesn't exist, it's that they find insufficient evidence in
humans to justify establishing the term in the medical literature. Catch 22: It is obviously not ethical to conduct tests with addictive substances on humans. All tests have to be conducted with animals.
Also, studies in more recent years all lean towards indeed comparing sugar to other drugs that have dopamine deficiency as a withdrawal symptom (it's a lot less addictive than most drugs, obviously, but once the neccessary saturation for an addiciton has been reached, they find the withdrawal symptoms to be comparable).
So while I admit that there's some maneuvering space there, your off-hand dismissal just simply doesn't cut it.
Here's one study from 2016 that argues
against sugar addiction:
https://link.springer.com/article/10.1007/s00394-016-1229-6/#ethics
Their flagship argument is that the observed behavioural changes in animals can be explained by other means. That's pretty much all of it. Not that there were
no behavioural changes or anything like that, merely that there might be other reasons for it than addiction (in their words, "most likely", that's as far as they're willing to go).
Here's one that argues decidedly for it, from 2018:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234835/
Compared to older studies, which were mostly behavioural, this one focuses on neurochemistry. I'll just leave the introductory statement from the conclusions here:
I could post several more studies that consider sugar addiction to be likely, but I think this is the most poignant one, and also one of the newest ones. In order to post more studies arguing
against sugar addiction, I might have to do quite a bit more digging. They're nowhere near as numerous...
So, if you'd have said "The subject of suggar addiction isn't quite clear-cut, and I tend to believe the conterarguments", I'd have cut you some slack. However, you said that there is
no scientific proof, which is just flat out wrong.