'Sugar free' drinks and glucose monitors - reliable?

Writing this in a bit of a tizzy, forgive me if it's a mess lol. Put in heavy topics for precaution since I feel like my world is ending (I know it isn't! But it feels like it) and I don't want anyone else to get in their head w/ this line of thought.

So, I go to 7Brew 1x a week. I really dislike having other people make my drinks bc I don't trust that in the rush of busy hours they'll give me sugar-free when I order it as such.

Recently, for my peace of mind (so I can still enjoy my weekly beverage), I've started using a glucose monitor and dipping 1-2 test strips into my drink to make sure it reads 'LO' or gives me an error.

I forgot my testing kit today, so I couldn't dip into my drink while I was out. I did the sticky test and it wasn't sticky, but when I got home, my glucose monitor read my (diluted) drink between >!60-90 mg/dl !<instead of flagging for an error/low.

I retested by dipping a different sugar free drink (bottled) to make sure my device wasn't glitching, and it read that one as 'LO'.

Is it possible that the sugar-free Torani syrups show up on the monitor if there's enough put in there, or maybe the sugar free energy..? I've never, ever had this happen before. The reading was still quite low (all things considered), but my drink was fairly diluted by that point, so I feel like it's a done deal :-(