The main point of dryfasting is to be healthy. It would be better and much easier for your body to process healthy foods after going through such a state. I personally just finished a 63 hour fast and had some grapes then a big salad. Even though I haven’t eaten for 2 1/2 days I feel full and energized.
To answer your question about smoking—yes. It stands to reason that it’s even worse for you in a fasted state. Take alcohol as a comparison. When fasted, a small amount has a huge effect. I wouldn’t do any drugs while fasting or take supplements, especially dry fasting. Could wind you up in the ER or damage your health in a big way.
You should ease your way in after any lengthy fast. Just as the body slowly adapts to no consumption, it adapts back to consumption. The longer the fast, the greater the stakes of not doing so.
I usually break my fast with Pellegrino water then eat a steak or any red meat 4 hours later. If I try to break my fast with eggs or cheese it will give me the runs. Everyone is different and will react differently. As many said, the idea of a dry fast is to detox and for health. Losing weight is the bonus.