Hello. We took a travel kettle and tea bags for the cabin and it was the best decision we made. Make sure you have an adapter though. They have 220 volts but the sockets are round 2 pin typ.
There are no tea making facilities in the cabins, and none on board after about 20.30. I took a thermos and filled it before that time. But if you like decent tea, do take your own tea bags and use the hot water still to make it. Likewise if you want decaff coffee.