[center][b][color=fff79a]Gray Sterling[/color][/b][/center]
Gray would eventually head to the bar for drinks (I mean, it's a party; even if there's no booze, it is etiquette to have a drink in hand to signal your turn to talk), and he would find they'd run out of cups. Honestly, not unexpected given how Voss' fan club seemed to have grown in the past while, but that still leaves him with a simple issue with a simple Sterling solution.

There are no unoccupied cups, so whose can he take... A mental list of who's here almost immediately bottoms out when he considers how petty he'd have to be to bother others for it, let alone resort to debts.

So that just leaves Voss and another, since he's an option. Yusuke, a guild member and another fan of Voss. Usually, not even worth considering getting involved with her, but if he baits her with her idol, that changes the picture. And if it's messing with anyone, he has to get Mio in on it too to make it practically guaranteed. 

A full plan organized in his mind to get a cup with just a few choice words...But, he cannot forget that they are still all fellow guild members. They're all practically family.

So, he sits beside Voss with a cheeky smile and glittering eyes that his fellow pretty boy would recognize. He's getting threatened.
"Vooooss, we're out of cups, share with me or you'll have to share with Yusukeeee~." 

It is important to note that Yusuke doesn't share. She either chugs it all herself or, as Voss knows first-hand, bashes his teeth with it to force him to chug all the sa- actually even worse now that Gray's remembering the last time he pulled this stunt. She couldn't stop giggling then, so she spilled it all over Voss...well, at least it's an effective threat to make.