Morning Fasting MBR if You Drinking Coffee or Tea

I'm just curious. Why would coffee, assuming your drinking it in the morning and not drinking it at night, affect your fasting number. I've noticed that my fasting readings are often the highest in the day. I am trying to figure out why.. I infrequently drink coffee in the morning. However, I frequently drink caffeinated iced tea in the afternoons. Is the tea you drink all day caffeinated?

I think I just figured out a way to keep my morning fasting number low, though I may have already shared this, but now I'm even more convinced. I gave up coffee. My husband needed to give it up for gastic reflux. So I changed to a coffee substite (Teecino). ANyway, Since then, my morning reading, and even some of my daytime readings, have been under 100, even low 90's and sometimes 80's. I haven't changed anything else. At first I thought it a fluke, but now, several weeks into this caffein-less regimen, I have to say it must be this. I remember also that every diet I ever was on said that caffeine, a powerful drug in it's own right, interfered with a lot that goes on in the body. I do however still drink tea, black tea and fairly strong, all day long, it's my beverage of choice. So that would be the other change in my diet. But I haven't had any tea for two days now, and I'm still low in the morning. I believe the caffeine in tea is different than the caffeine in coffee. Just my two cents