For a tea or coffee lover, a stainless steel insulated travel mug is great for keeping drinks warm and safe while on the go. Plastic-lined ones are not as good as steel, as they become stained and drinking from heated plastic is nasty.
I used to carry hard-plastic coated ones as they look nice, but they break inside of luggage too easily (photo of this type on right). Now I look for ones with double-walled steel construction, ideally with some rubber-like substance on the outside for insulation and gripping (see left photo).
I get mugs without handles, as the handles just get caught on things and take up unnecessary room in a suitcase.
You may get some side-eye from people from small-drink cultures that disapprove of North American gigantic mugs, but, oh well, ya can’t please everyone.