I wouldn't be worried about 1 cup of tea everyday. I live in Australia and pregnant woman here do not avoid any food apart from those at a high risk of infected disease (cold ham, cold luncheon meat, prepacked salads, raw meats and seafoods) and alcohol. Even with coffee, it is said OK to drink 2 cups a day. The reason on that is caffeine might reduce the absorption of iron in your body. So, I guess a cup of coffee or tea everyday or every few days are perfectly fine. I don't know if you have decaf tea and coffee in HK. They taste almost the same as the caffeinated ones
Apart from alcohol and raw food, I eat anything I feel like, all fruits, KFC, McD...as long as they are clean!!! Don't worry and be a happy mama-to-be