Sugar water and junk food taste good and people like myself crave that sweet flavor.

If I'm not careful, I can easily and comfortably guzzle liters of soda in a day.

It's less a hard thing and more a "I'm on autopilot right now, I'm thirsty, and there's a can of soda in the fridge" thing. A similar thing happens with junk food. If I'm hungry, on autopilot, and it's available. I'll probably grab junk food because it's fast, convenient, and tastes good.

You are abnormal for not being able to finish 1 can of soda in a year. Nothing is wrong with you for being like that, you are simply an outlier. There's a reason why Coke is one of the most wealthy businesses in the world.