If you're after that bitter taste, chicory is an option. You can compose it with milk and everything like coffee. The taste is a bit different, more herbal (which makes sense…). Sometimes I add a bit of cinnamon to it, that marries very well. But it has no caffeine. I almost fully replaced my coffee consumption already. One of its benefits is you can totally have a cup before sleeping!

It is common to mix it with coffee by the way!