In a medium pot, add 6 cups of the cold water and the sugar. Bring to a boil, then remove from the heat.
Add the tea bags and steep for 10 minutes undisturbed.
Remove the tea bags (do not squeeze them, or else the drink will be cloudy) and add the remaining 4 cups of cold water.
To make a tea, add 4-5 lemon slices to a large cup. Add ice and fill with the sweetened tea. Serve with a straw, and make sure you poke the lemon to release the flavor. Enjoy!
Notes
P.S I know the sugar amount sounds crazy but if we are replicating the Hong Kong cafe then you should add the full 1 ½ cups otherwise it will not be sweet enough.