Sometimes it's the food you eat if you are breastfeeding or the formula milk. Otherwise please seek medical advice as it might be some underlying urine tract infection.
As they grow up they urine will be like adult urine too? Food intake is a consideration too. But it is something really foul then I think u need to see a doctor
As they get older, their urine will stink due to the food they eat.
Food we eat. We are what we eat!