What should I send? It's up to you. Is the teacher a man or a woman? If it is a man, observe his hobbies, such as smoking. It is definitely more appropriate to give him cigarettes (but cigarettes are not easy to buy, and the whole thing is more expensive).
Of course, it is most suitable for daily use, such as apples and milk. I'm glad who gave me this. But if it is inconvenient to take heavy gifts, choose light ones. For example, a gift card of 200 yuan can also be considered.