I can give you the recipe now. I make diet coke chicken a lot. Just thinking about way to buy for te raffle next week.
Dice an onion and any other veg you like (mushroom, courgette, aubergine, carrot, etc). Fry off the onion in a saucepan in fry light, add the chicken (or quorn), stir fry some more, add the veg and fry off for a few more minutes, add a can of coke, 8tbsp passata, a few dashes of wostershire sauce. Bring up to the boil, then down to a simmer for 20 minutes or so until it has reduced. I serve it with rice, it is good with a jacket potato too