Ryanair has no limit on the number of vapes you can carry.
Ryanair allows passengers to bring vapes on board, subject to the following rules:
Vapes should be carried in checked luggage and may not be carried on a carry-on or placed in carry-on luggage.
Vape batteries should be removed and placed in carry-on luggage and not in checked luggage.
If a passenger needs to carry more than two boxes of vape, it is recommended that the vape be placed in the checked baggage and the battery removed and placed in the carry-on baggage to avoid problems at the security check.