Lily nods politely to a senior handing out water. "Excuse me, would you like coffee? I have a kilo of grounds and an enchanted moka pot, if you'll give me the water to brew it you can have three free cups with sugar, I have that too. No? Alas. Excuse me..."
It only takes her three seniors before she finds someone willing to take her offer. She takes the jug of water offered, and hauls it over to a table (making sure to check under it beforehand, and stay away from any vents.) She sets her pack down on the floor, puts her leg through the strap, and starts digging into it. Coffee grounds, enchanted moka pot, cups and saucers, package of Peek Freans -
There are 22 cookies, five plates, and five cups. She splits the cookies five ways, four to each plate, gives the extra two to the senior she offered coffee to as an extra for being a good sport, and with some mental math problems sets the enchanted moka pot to boiling. She pours coffee, and gets out her little tin of sugar from her spice collection and sets it in plain view.
"Free coffee and cookies!", she calls. "Warding, blasting, endurance and storage bracelets! School supplies, fine clothes, chocolate and spices! While supplies last!"