I'd like to know this too. We had sodastream growing up too- loved it. I think my mum still has the machine- and hopefully the bottles too. It was always cheap and easy for us to replace the gas in the cylinder cause dad worked at a gas company at the time, but i think my mum made some up not so long ago and she said it was a little exxy for the gas. We use to use cordial for the flavours and you recycle the bottles (we had glass ones). They were nicer and it was half the fun just making it. So might look further into myself too- will let ya know how i go.