As the poor left the bakery with their dinners, the spirit sprinkled each dinner with what? From his?
As others have said, the spirit, who is the Ghost of Christmas Present, sprinkled the dinners of the poor with drops of incense from his torch. This incense is the Christmas spirit of good will. It stops people from quarreling and puts them in a good humor.
Scrooge asks the Ghost of Christmas Present more specifically about what he is sprinkling:
“Is there a peculiar flavour in what you sprinkle from your torch?” asked Scrooge.
The Ghost responds:
“There is. My own.”
Scrooge then asks:
“Would it apply to any kind of dinner on this day?”
The Ghost responds:
“To any kindly given. To a poor one most.”
“Why to a poor one most?” asked Scrooge.
“Because [the Ghost answers] it needs it most."
The poor would need the spirit of good will and humor sprinkled on their dinners most of all because they would have the poorest meals and the greatest struggles to face and, therefore, the most to irritate and anger them in life. They would also have the most reason to be sad or despondent. The people who are entering the bakeries to warm their food do so because they can't even afford ovens of their own, and for free or for a small fee, can use the residual heat from the bakers' ovens.
The Ghost is demonstrating to Scrooge that there is more to life than accumulating the most possible money. The poor are more than simply the lack or want their poverty causes. Often they can have more of life's intangibles, such as the spirit of good will, than wealthy people like Scrooge.
As the poor people leave the bakery with their dinners, the Spirit of Christmas Present sprinkled each dinner with incense, or the Spirit of Christmas, from his torch. He does this for the poor because the poor are the ones who need the Spirit of Christmas the most. In addition, his torch was very unusual in other ways, as it had the power to also shed drops of water from it and restore good humor to those it touched immediately. For example, should travelers jostle each other and become angry, a few drops of water on them from the torch would restore them to good spirits. The Spirit of Christmas Present was essentially spreading the peace and joy of the holiday, although Scrooge did take issue with him and even argued with him a bit.
The Ghost of Christmas Present sprinkles a type of "incense" on the meals of some of the people that he and Scrooge see on the streets. He tells Scrooge when Scrooge asks if there is a particular flavor to what is being sprinkled that it is his own flavor, i.e., the Christmas spirit. He gives it to those, he says, who need it the most because they have so little and are struggling to get by. The Ghost sprinkles the foods with this incense from his torch.