Disappointed there is no carbon dioxide injection. In the 90s till date in this corner of India, Mr Butler is a compact pure mechanical device which can make nose tickling strong sodas. If I were a soda fan, I would have DIYed and rejected the flat mop water that most commercial sodas have become.
I made Open Cola once, and hooked it up to CO2 canisters and a beer tap (the other tap had home made beer). It's certainly better than mixing with soda water or using a SodaStream.
A easy solution might be to mix the concentrate with sparkling/carbonated water?