Using cold spring water?
bottled water will make a difference to the taste especially if your tap water is below par (most of the U.K.)
tesco’s ashbeck spring is ideal for coffee making as it has the right amount of dissolved solids (120ppm) and acidity and at £110 for 5 litres so cheap. its not what the name ‘spring’ suggests though, its tap water put through an industrial reverse osmosis machine which strips everything out and then puts the desired minerals back in. basically what coffee shops do for their coffee machines on a smaller scale.
is that a snobby/poncey/****/geeky enough answer for you?
i like cold brew in the summer especially with good quality fruity African beans, the pre made stuff is a bit hit and miss imho though i like the Sandows and the fresh daily made stuff in good cafe’s. the cans of nitro cold brew are not to my liking though.