Dreams can often reflect our subconscious thoughts, feelings, and experiences, and yours seems to involve themes of identity, boundaries, and perhaps a sense of violation or discomfort in a relationship.

1. Identity and Role Reversal: Dreaming of being a man in your early twenties while in a college setting may suggest you’re exploring your identity, independence, or aspirations related to adulthood. It could also indicate a desire to experience life from a different perspective.
2. Boundaries and Trust: The act of someone urinating in your water bottle can symbolize a breach of trust or violation of personal boundaries. Water often represents emotions and the flow of feelings, so this act might be reflecting a fear of having your personal space or emotional well-being disrespected.
3. Confusion in Relationships: The uncertainty of whether the man is a random person or your boyfriend may indicate confusion or anxiety surrounding your current relationships. It could suggest you’re questioning trust or the dynamics you have with those close to you.
4. Emotional Reaction: Your strong emotional response upon recalling the dream indicates that it has left a significant impact on you. Consider reflecting on any real-life situations that may relate to feelings of discomfort, trust issues, or identity exploration.

In conclusion, this dream could be encouraging you to examine your feelings about relationships and boundaries, as well as to explore your own identity and how you relate to the world around you. If you continue to feel troubled by the dream, journaling about your emotions or discussing them with someone you trust might provide further clarity.