Upvote:9
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 your purpose during your travels.