Cantonese Milk Tea
Under the influence of British Tea, Cantonese milk tea was invented. It is made of red tea and evaporated milk or condensed milk. It gave the habit of going out for afternoon tea to the people in Hong Kong.
Hong Kong Breakfast
As a colony of Great Britain, it change the way Hong Kongers have breakfast. It is common to see Hong Kongers having eggs, ham, sausage, bread, etc. in their breakfasts. It also kickstarted Cha Chaan Tengs making it one of the signatures of Hong Kong.
Egg Custard Tarts
The war also brought over pastries such as the egg custard tart. You can find it in Cha Chaan Tengs and most Yue Cuisine as a Dim Sum. There is also the Portuguese version of the egg custard tart which was introduced to Macau. Since Macau is fairly close to Hong Kong, you could find the Portuguese version in some parts of Hong Kong too.