Welcome and thank you for your questions. You should get current measurements close to zero for distilled water, but somewhere between 30 and 100 milliamps in some of the drinks. Your readings seem to be about 3 orders of magnitude low. Set your multimeter to the 200 milliamps range, or make sure you aren't mistaking microamps for milliamps. Remember, digital multimeters read back in the range setting they are in. For example, a reading of 1.0 in the 200 milliamp setting is 1.0 milliamps, which equals 0.001 amps (or 1000 microamps). Also, you should get in the range of 2.0 millisiemens for OJ and Sports drink.
Suggestions: Double check your circuit for proper configuration, ensure your multimeter is on the right amp range setting, ensure you use a reasonablely fresh 9V battery for all the tests.
For additional accuracy, if you have access to a second multimeter, you could also measure the DC voltage across the electrodes inserted into the drink specimen and use that value in your calculations instead of just assuming 9V.
As a side note for this type of experiment, there seems to be a relationship between conductivity and temperature of the drink specimen. For even more accuracy, you might consider making sure all your testing fluids are at the same temperature at time of testing as an additional control variable.
Hope this helps.
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