Readers reply: Why is sugar-free tonic water always described as ‘slimline’?

The long-running series in which readers answer other readers’ questions on subjects ranging from trivial flights of fancy to profound scientific and philosophical conceptsThis week’s question: When does a reasonable train route become unreasonable?Why is sugar-free tonic water always described as “slimline” (at least in the UK)? As far as I know, every other sugar-free drink takes the label “diet”.…