Ryanair doesn't seem to have fully embraced advertising opportunities on sick bags. With no seat pockets on their aircraft, sick bags are only generally available if you ask for them, and even then they are just plain white ones with no logo. A few years ago, they did have adverts for a photo processing company - so if you didn't throw up, you could send your films off in the sick bag to be processed. They might get some ideas from here:
Sick Bag Examples