If you are out at a supermarket, do not buy junk food. If you have junk food lying around the house, there is a good chance that you will eventually consume it. Not purchasing this food in the first place is the best way that you can prevent this from happening.
If you are trying to cut down on the amount of soda that you consume and think water is too plain, try flavored water. This tasty alternative comes with the same amount of water that you require, and does not have the high sugar and calorie content as soda.