What you are looking for is something called a "Seltzer Bottle
". Have fun exploring ... basically - it's a vessel that holds water, has a CO2 cartridge, and when you press the button - it carbonates
the water as it forces it out of the vessel. It certainly isn't "FREE" - but it can be cheaper than buying bottles of club soda and having them go flat. These were REALLY popular back in the 1930-1950 era - but kind of went the way of the fondue pot.
Limes are bitter - even true
Key Limes. And, I'm always skeptical about anything
claiming to be "Key Limes" = 99.5% aren't. A lot of unscrupulous marketers try to pass off just any small immature lime as being a "Key Lime" because it has become a "catch phrase". True "key limes" are small, but they are also a certain strain of lime trees that only grow in the Florida keys.