Today is Demi Lovato's 19th birthday ... and she kicked off the celebration last night by hitting up a local grocery store for a case of beer with her presumably-over-21 friend.
Lovato went to rehab last year, but her people said it was not for drugs or alcohol related issues.
For her part, Lovato tweeted last night, "Birthday redbulls cause #soberissexy... Duh. :)"
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