I'm not sure about Dan bringing her coffee but in 1x02 Serena showed up to Blair's with two bone-dry cappuccinos and in 2x23 also it's 発言しました in regard to Serena that: "She's not a morning person but 表示する up with a bone-dry cappuccino, she'll follow あなた anywhere." So I presume she primarily drinks bone-dry バッジ :) hope this helps x
