Try roasted barley tea, Postum (is is still made?), different herbal blends. . .
You could try rooibos (red bush) or honey bush tea. Nothing really tastes exactly like coffee or real tea, so I have found it is a matter of trying many different types of teas/herbal blends/coffee substitutes to find something that I like the taste of. Plus, give the non-coffee stuff a while for your taste buds to get acclimated to it (go cold turkey off of the coffee or decaff coffee).
A question if I am not too nosy in asking it: Do you find that decaf coffee makes your blood sugar swing *or* that you do not like the flavor of decaf or do you want to avoid the (usual) chemical(s) used to decaffeinate coffee.? If it is a flavor (or lack thereof) of decaf, try different styles/roasts/grinds of decaf coffee, or brew it stronger or try cold water extraction. If it is the chemicals, look for carbon dioxide decaffeinated coffee.
And of course you must look at what you put *into* your cup of coffee as well. I am not saying that you do this but some people put a LOT of sugar or sugar substitute in their coffee, and of course the sugar affects your blood sugar (and they are finding that sugar subs can do this also).
When I go for a hot drink in the evening, I use a good quality decaf coffee or some spiced redbush (rooibos) tea and I will be danged if an Irish Coffee doesn't taste fine with coffee maded from good, freshly ground, decaffeinated beans.
I find that as nothing tastes like something with caffeine in it because there is a certain "bitter" component of taste added by caffeine; this makes decaf coffees/teas taste like they are too "soft" to me. So, sometimes for me (and maybe for you?) it is best to go with something completely different tasting, and go cold turkey off of the coffee or "real" tea.
Consider it an adventure and have fun and good luck finding something new to drink in the morning!