Pola

The bin list, since slime by itself is not it: fuzzy mould on the surface or on the beets, anything pink or black or otherwise colourful, a smell that is rotten or putrid rather than earthy and sour, or beets gone soft and mushy and smelling bad.

You have ruby colour and an earthy sour smell, so this is texture. For reference, good kvass should be salty, earthy, slightly sour and clean. Sweet, flat and slimy is the combination that means start again.

Slime on its own is not the dangerous signal, and your own description already covers the ones that are. Bin it immediately for fuzzy mould of any colour on the surface or the peels, anything pink or black or green or otherwise colourful growing, or a smell that has gone rotten or putrid rather than sweet and sour.

You have sweet pineapple and no fuzz, so this is a texture problem. And genuinely, if you are ever unsure, throw it out. Pineapple peels cost nothing.

Worth being precise about what you are checking for, since vinegar smell gets treated as a warning sign and is not one. Acidity discourages most of what you would actually worry about, which is why a sour jar is in less trouble than a sweet neglected one.

The bin signals are fuzzy or coloured mould, and a smell that is rotten or putrid rather than sharp. Sediment is just yeast that has settled. Sharp and clean plus a bit of sludge is a jar that needs feeding, not throwing out.