england-and-wales
No.
Alice bought (a jug of) water in the café. She left water in the jug, left the jug on the café counter (or table) and then exited the café (without asking to take the water with her) - these are signals that she 'abandoned' the water. It's the same as if she left a half-eaten sausage roll, a half-consumed coffee or crumbs from a Danish pastry.
There's no 'theft' in taking something abandoned.
Had she entered the café with something she went on to leave in the café, perhaps she brought in four bags of shopping and left with three, or she left her umbrella, handbag, mobile phone or car/house keys, then it doesn't seem reasonable to immediately assume it was abandoned and we get into having to make a reasonable effort to find the owner.
Whether something has been 'abandoned' can sometimes be difficult to establish. A classic case is items in a household bin; or items left outside a charity shop or by the bins behind a charity shop (Ricketts v Basildon Magistrates [2010] EWHC 2358). Law SE had a question (and answer) about (not-)abandoned newspapers.
In the absence of case law, I suggest that in the scenario of a café or similar place, if the customer orders some food/drink, leaves some of it, pays the bill and exits the establishment, without signalling any further interest in the food/drink, it seems reasonable to assume the customer no longer has an interest in the food/drink and has abandoned it.