THIRST-E is a drink-dispenser-bot aboard the Axiom. Just like SAUT-A, THIRST-E is seen in the old Axiom commercial video.
In the video, THIRST-E is seen on the Lido Deck with BRL-As, VEND-Rs, SECUR-T and the passengers. It is likely that VEND-Rs go to THIRST-E to fill the cups they serve to the passengers.