You should come clean and then deal with the consequences. You made a mistake it's okay. we all do. the important things is to learn from our mistakes and face them. If you talk to the people who are involved in this incident then they might allow you to return the money when you get it (this would mean getting a job or something.). Explain how you feel and what happened. Being honest is the only way to lift this weight from your shoulders. It's not going to be easy but you can do it.
Be mature. Atleast you know you did wrong and you can only learn from this. I'm sure that if you are honest your friends will understand. Just open up and don't be afraid to show your emotions.
Why do you think you are going to Jail, though?
Best wishes!
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You'll never get to heaven if you are scared of getting high.