For proper absorption and optimal results, Step 1 is best taken on an empty stomach, so pairing it with bulletproof coffee would interfere with that. 30 min. is the minimal time to wait after taking Step 1 before adding any food or drink, since that's the time it takes water to leave your stomach, so all the ingredients are diluted and absorbed by your system.
Pairing Bulletproof coffee (or something similar, such as coconut oil/MCT/coffee) with Step 2, however, can be a great combination that helps facilitate proper Step 2 absorption and optimal effects. The nutrients in Step Two, especially the B vitamins, can be intense on the GI tract if taken without food, so for best absorption as well as avoiding stomach sensitivity while optimizing the effectiveness, healthy fats such as those found in coconut oil are a great compliment to one another.
Everyone's digestion and absorption needs are different, however, so you may find that in addition to Bulletproof coffee, you also need to add additional food to aide absorption and avoid avoid any stomach discomfort.