All of them (the descendants of Vrsni and Bhoja), being permitted by the brahmanas, partook of the remnants of prasada and also drank liquor made of rice
SB Canto 3
Thereafter, all of them (the descendants of Vṛṣṇi and Bhoja), being permitted by the brāhmaṇas, partook of the remnants of prasāda and also drank liquor made of rice. By drinking they all became delirious, and, bereft of knowledge, they touched the cores of each other's hearts with harsh words.
In ceremonies when brāhmaṇas and Vaiṣṇavas are sumptuously fed, the host partakes of the remnants of foodstuff after the guest has given permission. So the descendants of Vṛṣṇi and Bhoja formally took permission from the brāhmaṇas and ate the prepared foodstuff. Kṣatriyas are permitted to drink at certain occasions, so they all drank a kind of light liquor made of rice. By such drinking they became delirious and bereft of sense, so much so that they forgot their relationship with one another and used harsh words which touched the cores of each other's hearts. Drinking is so harmful that even such a highly cultured family becomes affected by intoxication and can forget themselves in a drunken state. The descendants of Vṛṣṇi and Bhoja were not expected to forget themselves in this way, but by the will of the Supreme it happened, and thus they became harsh towards one another.