Sugar dropping.

Thursday I did my gestational diabetes test and felt like complete crap all day after well today I went to Kroger and drank a medium vanilla bean frappe while there it took me at least an hour to finish. I got home and started cleaning up but I felt really off and my hands were shaking so I checked my sugar and it was 60. Does anyone know why it could drop to that number so quickly? I took my sugar after my gestational diabetes test to see what the difference was between their blood draw and my meter (still haven’t gotten results) at the 1 hour mark it was 160 on my meter but I’m waiting to hear my actual results from my OB. Is there anyone with experience in their sugar dropping after just having sugar? I read it can drop fairly quickly in women with gestational diabetes but that just makes no sense to me.