* Sweat: While most mammals sweat, there are some exceptions. For example, monotremes (like the platypus and echidna) don't have sweat glands. They cool down using other methods, like panting.
* Live young: This is the defining characteristic of mammals. All mammals give birth to live young, unlike reptiles, birds, fish, and amphibians who lay eggs.
* Milk: Again, this is a defining characteristic of mammals. All mammals produce milk to nourish their young.
Therefore, there is no mammal that fits all three criteria.
It's possible you're thinking of a different group of animals, like reptiles or amphibians, which might not have all of these traits.