According to my TA, there are London Dispersion but I'm unsure if both of caffeine/DCM and caffeine/water interactions go through them as the dominant interaction. In DCM, I'm pretty sure there are dipole moment between Carbon and Chlorine. One chlorine is pointing up and the other one is pulling more downwards, these two dipole moments doesn't cancel each other out so it makes DCM kind of/ partially polar. For the other interactions between water and caffeine, well there's definitely london dispersion and hydrogen bonding, I'm not sure what else so I guess those are the two for water/caffeine interactions. I guess now I'm not 100% sure about caffeine/DCM interactions. Thanks BabcockHall.