How can I cool tea quickly? Imagine you're making someone a tea, but for whatever reason they have to leave soon. How can I cool the tea so that they don't have to choose between leaving it unfinished or burning their mouth? Ideally the method should not only be fast, but also let me reliably reach about the same temperature every time.

I've thought of the following:

Add additional milk - cools tea, but affects taste.

Heat the water less - won't make tea as hot, but might affect how well the tea infuses.

Add cool water to boiled water - would cool down a fully-infused tea, but hard to control resulting temperature.

Put it in the fridge for 30 seconds or so - would cool tea, but seems like a bad idea.
What is wrong with a regular ice cube? As you state that the tea is not yet ready, you just use slightly less water and then add the ice cube, which has a fixed temperature.

I use this for large scale ice tea production. As I use 1:1 hot water : ice cubes I simply brew a double strong tea.