when you were a tenager, where did you hide your drinks?

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We are painting the children's room and wife asked me to remove the air register. I removed it and I noticed an object inside. I reached to see what it was and this is what I found.

The previous owner had a teenage son as far as we understood. My guess is that he put it there. Or maybe from the owner before them. I tried to find an expiration/manufacturing date on the bottle to get an idea of how old it was, but I couldn't see one.

If you were hiding drinks from your parents when you were a teenager, where did you hide them?