What does it mean to dream that someone gave me a cup?

Glass has many characteristics: fragile (which can indicate poor personal endurance), transparent (pure), flowered (romantic), uncovered (to show you a clear head) and accommodating (to hold water and preserve health and wealth). So there are many symbolic meanings. It can be derogatory or positive. So this dream must be in line with other dreams that night, in line with your usual relationship with him, and make further detailed explanations.

If you are a girl and he is a boy, it is a symbol: glass represents his pure heart, and with his flower-like romance, it opens an open heart to you and gives you a lifetime of wealth and happiness.

It's just your subconscious. In reality, whether he really means this to you, you should carefully distinguish it, and don't let your subconscious mind have illusions and misunderstandings (of course, the subconscious mind is inspiration, which is generally more accurate)!