Specifically, if you buy something at a participating Starbucks in the morning, you can bring in the receipt for that purchase on the same day after 2 PM and get any grande cold beverage for $2.50.
Most grande beverages at Starbucks go for at least $3 and up. Grande cold beverages include iced coffee, iced tea, Starbucks Refreshers, and Frappuccinos. If you really want to squeeze out as much value as you can on the second drink, you could probably custom order a Frappuccino that would normally cost $5 or more.
If you don't have your same-day receipt but paid with the Starbucks mobile app, you can also show your history from the app to take advantage of the offer.
Photo via Starbucks.