Step One: Purchase teabags in bulk.
Step Two: Obtain 16-20 glass bottle. I have found Welch's juice or Snapple bottles work great(note wide mouth)
Step Three: Place teabag in bottle so that the string remains out and will be held in place by the cap.
Step Four: Fill with cold water and apply cap. NOTE: Do not shake the bottle as tea will escape the bag making a mess.
Step Five: Place in refrigerator or on counter for 8-12 hours.
Step Six: Remove Teabag and shake before consumption.
If a stronger taste is desired, try using two teabags at once. Use this method for any tea that does not require HOT water.
I started using this method to steer clear of drinking soda, yet still having the ability to take the drink with me.
Be sure to wash your bottle around every 3-5 uses to avoid bacteria buildup.