Not sure if this is relevant but there is a fast and simple way to make money through Starbucks gift cards.
Step 1. Contact Starbucks and tell them that your drink was not how you liked it. (Mention that you go there a lot and didn't want to bring it up to the manager)
Step 2. You should get an email back from them saying that they are very sorry. They will then give you the option to either charge up a gift card or get one sent to your house.
Choose the option to get the card delivered to your house.
Step 3. When the card arrives at yourself you can then sell it to people.
Note: This will work nearly everytime. But try and use a vpn to prevent suspicion.