Does anyone know any good experimental techniques of measuring refractive index of water?
Use a refractometer.
Not very helpful if you 1. Haven't got one, 2. Can't afford one.
If this is a school type of experiment that you're after then using Total Internal Reflection is a good approach because you can use readily available equipment. You might find this hyper physics link gives you an idea for a simple and cheap experiment.
Not very helpful maybe, but given the level of detail in the op...
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