things you need to look for when booking hotels at Dublin airport
Onsite V Near
The onsite hotels are
http://www.maldronhoteldublinairport.com/
I have stayed here a few times. Free 24 hour shuttle to Terminals, closet hotel to terminals, not sure about breakfast, but food outlets after security in both terminals open around 5am Very reasonable rates
https://www.radissonblu.com/en/hotel-dublinairport
Free 24 hour shuttle , breakfast included, little bit more expensive than Maldron
Offsite
http://www.carltondublinairport.com/
Website says 2 minutes from the airport but I have stayed here and it was more like 10 minutes from the hotel to terminal. Nice hotel with reasonable rates. 24 free hour shuttle, not sure about breakfast
http://www.premierinn.com/gb/en/hotels/republic-of-ireland/dublin/swords/dublin-airport.html
10 minutes from the terminals, no free shuttle, you pay the driver €1 on each journey. I have stayed here, nice hotel but would not be my first choice
These are the hotels I would recommend to anyone looking for somewhere to stay at the airport. You need to be careful when checking hotels, may say near Dublin Airport but may be anything up to 20 minutes away from the terminals. Check them on Google maps, and see exactly where they are located in relation to the airport. Any hotel that has Swords in the address is north of the airport, any hotel that has Ballymun or Finglas in the address is south of the airport.
I stayed at
http://www.claytonhoteldublinairport.com/ this year. It is about 15 minutes from the terminals. I found it a very tired, shabby looking hotel.
The Holiday In Express is actually about 20 minutes from the terminals. It is not one I would recommend for anyone flying / from the airport.