I’ve read multiple times people saying that Boaphiles and other cages made from PVC type plastics smell over time. They claim that no matter what they did, they could not get the urine smell out. Well, I’ve got a solution for you!
Take one gallon of water. I use an old milk jug. Add one ounce of bleach and one ounce of white vinegar. Shake to mix solution. Put this mix in some type of sprayer. I like to use a small hand held garden sprayer from Lowe’s. Spray down the inside of the cage and let it sit for a few minutes. After a few minutes, wipe down the entire inside and let air out. The small amount of bleach used should not leave much of a smell. If you like, wipe down the cage again with plain water.
Not only should this get rid of any smell, but it is one of the best disinfectants you can use!
Here are two good links for more information on using a bleach / vinegar mixture: