The main meanings of gift mugs are as follows:

Between couples: Giving a cup often symbolizes a promise of “a lifetime,” representing the deep bond between partners and their commitment to long-term companionship in the future.
Among friends: Giving a cup symbolizes deep friendship and enduring companionship, hoping to become lifelong friends.
Between teachers and students or between elders and younger generations: Giving a cup expresses respect and gratitude toward elders, carrying profound meaning.
Between customers: Giving a cup symbolizes a strong and lasting cooperative relationship.
The specific meanings of gifting a cup in different relationships
Between couples: Giving each other cups—especially thermos cups or matching couple’s cups—represents a promise of “a lifetime together” and symbolizes both partners’ wish to spend their lives side by side.
Among friends: Giving each other cups—especially thermos cups—symbolizes deep friendship and enduring companionship, with the hope of becoming lifelong friends.
Between teachers and students or between elders and younger generations: Giving a cup expresses respect and gratitude toward elders, carrying profound symbolism that embodies reverence and appreciation for them.
Between customers: Gifting cups to each other symbolizes a strong and lasting cooperative relationship, expressing satisfaction with the customer and the hope for continued collaboration in the future.