I went a bit crazy in sainsburys yesterday - they do three flavoured still waters with malic acid - cranberry and raspberry, apple and blackberry and peach. 70p per 1.5ltr, not on offer at the moment.
They also do a flavoured sparkling water strawberry and kiwi which has malic acid but that has apple juice in it so not sure if its ok? I bought some as it was on three for £1.20 (i think) but holding off on drinking it in case its BAD.....think it might be mentioned earlier in this thread so will have a look!