These days one can buy sachets of tea that contain some spices and are sold as Chai. Needless to say this comes nowhere near real Indian Chai.
I know you are supposed to cook the tea with the milk if you want to get the real thing, but apart from the fact I have no time for that, I also do not like the taste when the milk gets overcooked. And this happens very easily. On the other hand, taking the shortcut with the ready-to-go tea bag is a joke.
Some cafes here in Israel pretend to carry chai, but if at all they attempt to brew something that is more than just hot water on Wissotzky with optional milk and sugar, the result is so amazingly bland, I find it justified to publish my embarrassingly simple shortcut to chai.
up to 4 tea spoons sugar
half a teaspoon garam masala
half a teaspoon ground ginger
a quarter of a teaspoon ground cinnamon
3 to 4 servings of black tea
1 liter of boiling water
Throw the dry ingredients in a (pre heated) teapot. Pour on the water, then add milk till the color is right. Stir. Allow around 10 minutes of standing time.
A post scriptum on the issue of spices is in place. The quality of dry spices one is sold in the shops can differ amazingly and this can have a very significant effect on this tea or other cooking for that matter. Notorious, in my experience, are cinnamon and nutmeg, that can vary from tasteless to very strong. You have to be familiar with your garden variety and adjust the amounts in the above or any recipe to your taste and brand strength.
The same goes for garam masala, though the difference, being a blend after all, also lies here in the measures of the ingredients and how fine the spices were ground.
Last but not least, one can pick and choose the spices for this tea, or chai if you will. Other options are: cardamon, cloves, pepper, galanga, cumin and turmeric.