The idea of nicotine water is kind of weird. The human stomach doesn't digest nicotine well - it usually causes nausea - which is one reason why nicotine overdoses by ingestion are rarely serious or fatal. It's also probably the reason why you don't see nicotine pills or why
vaping too much, too fast and basically swallowing a lot of the liquid can upset the stomach. So, they'd have to keep the nicotine content in the water REALLY, REALLY low, so people wouldn't just throw it back up!