Not really a formal recipe here, but more for reference.
Take 7 tea bags and place them into a 1-gallon jar of cool water.
Place the jar into a sunny place and leave to brew for 4-6 hours.
Move the jar to keep it in the sun as much as possible.
Server over ice, lots and lots of ice.
Note, you can substitute different kinds of tea into the jar. I recommend green tea as well as any herbal tea you enjoy.
Experimentation is a good thing.