low cal tonic water?

Is tonic water allowed? I'm just trying to find an alternative to an alcoholic drink and I like tonic water better than diet coke

Drinks must be no fruit, no sugar and less than 1 cal per glass.

it's no good then cos there are 2 cals per 100mls

Oh, shame I've got Sainsbury's own brand Diet Indian Tonic Water here and it's only 1cal per 100ml. So maybe have another look in the shops - there are several diet drinks that fit the bill and contain no fruit(to have occasionally, max 3 can per day I think, I have about 3 a week so I'm not sure).