"You got a Tingle Bottle! Using Miiverse, you can insert a message you've written, and send it out to sea for someone unknown to receive!"
The Tingle Bottle is an item found in the HD remake of The Wind Waker. It replaces the Tingle Tuner, as the Wii U does not support Game Boy Advance connectivity, which the Tingle Tuner was a showcase for.
The Tingle Bottle was used to send messages to people via Miiverse. Link can write a message, and then throw the bottle out to sea, at which point it is sent to players around the world. This also worked the other way, as Link could receive messages from other players. Tingle Bottles from other players could be found floating in the ocean or on beaches. Pictographs could be attached to the bottles sent out and received as well, and any that came from other players could be saved to Link's Pictograph Box.
With the closure of Miiverse in November 2017, the Tingle Bottle now serves no purpose.