Okay. All of the above are rather weak incentives when compared with other things: discoveries, work, travel. You can continue the series with a variety of activities that are incomparably cooler. Not so much pleasure all of the above, if you evaluate objectively. Rather, a cure for boredom, for not understanding what to do.
Somehow you are all in one heap in the way. These are fundamentally different things.
Cigarettes are a disease. It is not "tasty", not "entertaining", not "enjoyment." Cigarettes are a drug that relieves withdrawal symptoms in people with acetylcholine receptor disease. It is strange to count them as "small treats" along with sweets. Moreover, billions of people who do not suffer from nicotine addiction do not use cigarettes and do not feel craving for them. Do you think they are "bored" without nicotine withdrawal?
Sweets are different. There are better ones, where there is usually less sugar, and "consumer goods" from the nearest supermarket. From experience I notice that when I stop eating especially thermonuclear sweets (Milka or Alpengold chocolate, Snickers, Marsa, Bounty), after a while I stop being drawn to them. The body does not want such sugary products, and asks for something easier - dried fruits, nuts, etc.
Alcohol. Here I am not a great specialist, but I see no reason to give up alcohol completely. A glass of wine at lunch or a glass of beer on a hot day is both pleasant and not so harmful. When people completely give up alcohol for no serious reason and without an inner desire, they can be uncomfortable. The culture of drinking table wines is several thousand years old. It is not at all necessary that the person who shares it is a complete drunkard and socially dangerous element.
"Junk food". This word combination jars me. This is a label that people are used to pinning on any dishes, sometimes without thinking too much and contradicting themselves. Why should this the day before yesterday "grandma's cutlet" from the purchased minced meat be better than the McDonald's cutlet? Why should this sticky pasta and ketchup brew be better than pizza? (but home!). The body is not a fool. Sometimes he needs katle-e-ets, and hamburgers, and broccoli, and chips. The division of food into "bad" and "good" is an exaggeration that poisons the lives of many people.
In my personal experience and understanding: I have never smoked, there is nothing to compare with, I am only happy about this, for a lot of reasons.
Alcohol - in large periods when I did not drink / do not drink at all, life no worse. Alcohol for me is a way of situationally hammering the experience of stress. This is not so valuable, and potentially not very much.
As for food, I have been following my figure for 13-14 years, I regularly limit myself to food, but even during these periods I eat whatever I want. I am a former doctor, and I do not know "junk" food. The harm can be in the absence of boundaries in quantity.
From personal experience: You shouldn't mix all these things together. 1. Cigarettes are better without them. That is, it would be better not to start. 2. Alcohol and other psychoactive substances. You can experiment, but with great care. Everything is very individual. Someone all their lives calmly drinks themselves and rejoices, without causing harm to anyone, while someone drank themselves quickly enough, sliding to the bottom. Again, if it is good without it, then it is useless. 3. "Harmful" food - in my opinion, only what you don't like is really harmful. The body is not a fool and will figure out what it needs and what it doesn't. There is no sense in denying yourself food.