Am I allowed to take hot water from an urn into a cup, then pour that into another cup that has a tea bag and sugar in it on Shabbos? If not, how can I do it?
Thank you for your question.
The sugar in the second cup is not a problem but the tea bag in the second cup is. The reason it is problematic is because a tea bag is considered “kalei habishul” an item that cooks easily. Therefore it can get cooked even when hot water from a kli sheini is poured on to it. There are however a number of options. Either to make tea essence from before Shabbos, pour water into your cup and then pour the essence and sugar into the cup.
Alternatively, all though many poskim differ, the opinion of R’ Moshe Feinstein zt”l was that the tea bag may be placed inside the second cup AFTER the hot water was already poured into it. The reason this is different than pouring the water on to it, is because after the water was poured into the second cup, it is a kli shleishi (the pot was a kli rishon, the first cup a kli sheini, and the second cup a kli shleishi). R’ Moshe held that a kli shleishi cannot cook even tea.
M:B 318-39, Orchos Shabbos 1-74, footnote 165, Aruch Hashulchan 318-28, Chazon Ish O:CH 52-19, Shemiras Shabbos Khilchoso 1-57 (old edition), Igros Moshe O:CH 4-70. It is interesting to note that although it is permitted to make tea with essence in the manner described above, R’ Moshe writes ( O:CH 4-74 bishul 16) the when he personally makes instant coffee on Shabbos he only adds the instant coffee and sugar to a second cup, which is a kli shleishi.