I became more conscientious after learning of the 1974 WENELA C54E crash whilst serving in Malawi; this was further re-enforced operating with VIP flights and seeing the Fueler's sample being sealed and held by the policing authority on some airfields (most notably in India).
Without that, the syringe used to draw kerosene through a water sensing capsule was a good sniff test piece; the old style litmus test paper was left at the bottom of the testing jar..
When uplifting demin water I would taste a sample from the bowser, as most airfields at that time served demin and water methanol from similar browsers.
This crash happened post a refueling stop and that is the only reason I mention the above experiences.