You can keep a Latte in the fridge overnight and then reheat the latte.
If you have a left over latte and want to save it for the next day just place the latte in the fridge overnight and then reheat the latte in the microwave.
The latte may lose a bit of it's normal flavor but it will still be good to drink when reheated.
Because lattes contain milk, it's not a good idea to drink one that's been cooling for more than two hours.
If you know you're not going to be able to finish a latte for a while, it's best to put it in the fridge before the two hours are up.
When reheating the Latte you may want to add a bit of water or additional milk to weaken the latte as it can get a bit stronger when reheated.
Adding the bit of milk or water can help keep the Latte from becoming strong.
I've refrigerated lattes that I had leftover and reheated the next day and it's been fine with adding a bit of water or milk to the Latte.
I sometimes have coffee leftover and just leave the coffee out and then add a bit of water and reheat the coffee.