Yes, tried butter. Didn't like it. Also tried: Coconut oil - didn't like Beef tallow - really didn't like Bacon - ok. Bacon is suppose to make everything better, not coffee. In fact the coffee made the bacon better.... I don't find anything that makes coffee better, I like it black. However somethings do go with coffee for me (but don't make it better if that makes sense): Frangelico Chocolate Dates (eating with coffee, not mixing) Chilli especially habanero Four Pillars barrel aged As for bullet proof, I don't get it. I have tried but don't get the "all day energy" that people claim they get. What is the mechanism? Silence on that one.... :-| The only viable one I have heard was from Robb Wolf, that caffeine is lipophilic, hitches a ride with the medium chain triglycerides. The MCTs are processed differently to other fats, they go straight to the liver and are converted to ketones. So a slow burn with caffeine... But he was "searching" for a way not proposing that this IS how it works. So I made three espressos, one decaf, one 100% arabica, one 100% robusta. Added coconut oil. The oil emulsified the same in all... as in not at all. The only variables to how small the fat particles got was heat and agitation. I don't believe that caffeine is lipophilic, more that bullet proof coffee is a placebo.