Most people here recommend stopping something not taking into account that it may not last long. One slip and you're back. No addiction is cured by stopping immediately. You cannot simply get rid of a habit in one day. It has to be steady and progressive so that there's zero stress during transition.

First, start combining junk food with healthier meals. Like once a week, have something semi-healthy. Find something that tastes right for you. It may be not completely healthy, but the main thing is that you should enjoy it. Then start expanding it to more days per week. Repeat until the week days are all "semi-healthy" food. Next step, do the same but lean towards even healthier food, repeat the same process. Start marking cheat days on your calendar, when you can eat whatever you want. At this point you want to make eating healthy food a habit, and cheat days (1-3 per month) as an exception.

I used to drink lots of Lipton Ice Tea. First I switched to some other drink but with less sugar. Then I switched to Cola Zero. Then I started drinking mineral water. Now I basically drink just water and occasionally some Coke Zero. Same scenario also worked for smoking.

TLDR: steadily find better alternatives. Never make sudden change. Make it a habit. Rinse and repeat.