"After doing some research and searching I have finally got the answer to what Britney was drinking! It is a Ginseng supplement that gives you energy which also explains why she drinking it with red bull. I must admit it did look like a shot of liquor cause some of them come in those bottels but it wouldnt make sense! So all you people at "The Star" I bet you feel pretty stupid right about now because Britney herself confirmed it."
quoted from truebritney.com