This has been tested and WORKS.
Ok, boost is basicaly a store in australia (not sure if its in other countries) that sells smoothies and crushes and juices and things.
Basically you order a drink, tell them your name and they make it for you and call for your name to come get it a few minutes later. I'll describe how to get free drinks in a chat log below.
Note: This is a scam
Me: Hello, could i get a tropical Crush please?
them: Sure, that will be $5.25.
Me: Here you go.
then: Could i get yoru name on that?
me: Persian
Them: ok, please go wait and we'll get it ready in a sec.
***few minutes later***
Them: Did someone order a tropical crush?
*no one responds*
*they just leave it for someone to pick up*
**Wait a few minutes and they'll notice you've been standing their for a while**
Them: hey, um...what did you order?
You: a Mango Crush.
Them: Um...could i get your name please?
You: yea its Persian.
Them: Oh...Ok, we'll get it in a second.
*they get it ready and give it to you*
Them: We're very sorry for the wait, but we accidentaly made the wrong drink. Here, you want to keep this one too? No one ordered this, it was made by mistake.
THE END
So basically you got a free drink by pretending they made the wrong thing.
:P hope it helps you
~Persian