Citrus is the king of the winter fruits here. I have a number of earlier posts on various citrus cultivars with their ripening times. Here I have 5 different mandarins, Early Navels, Vainiglia Sanguino acidless oranges, Kyomi tangor, Cocktain grapefruit, and two different kinds of limes.
Besides citrus, I have tropical guava and dragon fruits now. I think it should be possible to have white sapote fruits in January too. I picked all mine in December, but my trees are young.
To my surprise, I am still picking dragon fruits and they are ripening just fine. This winter is very mild so far. Below are Sugar Dragon (left) and Halley's Comet.
Other options for January fruits would be very late persimmons and very late kiwi. I hope to get some of these fruiting in a few years.