You use the words "experiment" and "correlate" somewhat loosely in your question, but there are various ways that we can address the general idea in a more rigourous way. Let's consider two possible situations:
(1) You randomly put people into two groups and found that group A likes pepsi much more often than group B.
(2) You had an idea that people with, say, higher employment status would be more likely to like pepsi. So you deliberately split people into A (managers) and B (subordinates) and found that group A likes pepsi more often.
If the situation is (1), and the difference in preferences is a large one, then you might want to look at the groups and see in what ways they are different. It would be perfectly fine to observe that the groups were different on, say, BMI, and you could speculate that that is why one group prefers pepsi more often. But it wouldn't be very convincing because there could be many other ways that A and B differ, some of which you probably haven't even thought of or can't measure, and there is no way of being sure which factors align with preferences, let alone what causes them.
The situation (2) is much closer to a "true" experiment. Based on previous research or results you could isolate a particular factor and make sure that the groups differ only in that way. In more refined experiments you could try to exclude potential confounding variables (e.g., by making sure your managers and subordinates were all the same sex, and had equal BMI). Ideally, you could even try to manipulate the factor within the same participants and see if preferences changed (e.g., if a subordinate gets promoted, do they change their preferences when you test them a year later).