As the majority of the sodium for most of the products is in the flavoring packet, the most popular way to lower the sodium is to use less of the powdered soup or sauce flavoring packet. Start with less, and gradually add more until reaching the desired taste. 

For Ramen (bagged) and Instant Lunch (cup) there are two Less Sodium options in Chicken flavor and Beef flavor. Check with your local grocer for availability. Another option is to check at online retailers such as Walmart, Amazon, Jet, ShopFoodEx, etc.