Great question — answering as the UphillTech team:
Here's a site showing various electronic devices and a manual solution (test strips) that seems to solve your problem: https://mysugr.com/diet-drink-really-diet-check-sugar/ 100 test strips for $25 with the suggestion that you can cut them in half to last longer. That would probably last you a few trips and give you peace of mind. Here's another (old) site recommending the use of test strips: http://home.ptd.net/~hwagner/2r_strip.htm typically used to test urine, but could also be used to test drinks for sugar content. Here's a random site selling such strips: https://www.enasco.com/product/SB09754M though it might be adisable to speak to your doctor to determine if these should be used for...
Full answer by Berwyn: https://travel.stackexchange.com/a/69139 (CC BY-SA 4.0).
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