Green’s Dictionary of Slang

(drugs) a ‘bar’ of Xanax (alprazolam), used medicinally to counteract anxiety/panic.

2017		Guardian 17 Nov. 5/1: He is also filmed dropping bars of Xanax [...] Drake admits to having ‘Xans’ in an Advil bottle .
2021		Central Cee ‘The Bag’ 🎵 I’m the reason the party tun, when the party done, they’ll call for Xans.