Is sugar addictive? Like alcohol or nicotine?

Of course it is! But the withdrawal symptoms appear to be less! 

"This is a heavily debated topic. Alcohol, nicotine, and opiates are all classified as addictive substances based on strict clinical criteria, and although sugar has been shown to increase cravings and compulsive eating behaviors, technically it’s not classified as an addictive substance based on current clinical criteria.

But the physical and psychological effects are real.  ... That leads to habitual consumption, and when you suddenly stop consuming those foods, you do experience some withdrawal-like symptoms: headaches, dizziness, anxiety, and so on. But it’s a matter of the degree: For alcohol, nicotine, and drugs, those symptoms are very severe, and it’s very difficult for people to completely stop consuming those substances. ...

We need some sweetness in our diets and in our lives.

So we can say that sugar has some addictive qualities, but it’s not officially classified as an addictive substance like alcohol, nicotine, or drugs.

It’s also important to make a distinction between a food or nutrient that we need to survive versus a drug or substance which can be completely removed from our diet. You can eliminate alcohol or drugs, but sugar is in fruits, vegetables, whole grains, milk, and other dairy products. If you consume low to moderate amounts of sugar, it’s not going to have major health consequences or psychological effects. The most important issue is the dose. ..."

Is sugar addictive? — Harvard Gazette "Cravings are real, nutrition researcher says — but here’s why lumping sweets with alcohol, nicotine is a problem"