hot milk tea is more sugar and tea than the milk portion, would not worry to much, the msg and oil when you eat out is probably already shortened your life more than the milk tea.

by the way the milk tea is great mixed with brandy on a very cold day, cheers.

With those premade powders, you have less control on the quality of the milk, tea and additional stuffs like colorants. If you buy actual milk, prepare some tea, and add cacao powder, you might a little bit more sure, you will ingest less additives too.