If your flight is direct from Barcelona you can indeed buy a standard bottle of wine (or even several, depending on what country you go to.)
The limit to go through security is 100 ml per bottle, all bottles and other liquids have to go into the one liter bag.
After security you will find shops and they will seal the bottle in a bag to show you bought it from them.
This is not only Ryanair, this is common for all airlines which leave from European (and other) airports.
On the other end of your journey you will need to go through customs, (even when flying within Schengen.) Best check the information for your country (which you do not mention) to see how much you may bring home. If you want to buy more, you have to go through the red channel and declare what you bought.
I checked this site by IATA and it looks like you can bring twenty liters of wine or ten of stronger spirits. This is for Portugal but would also be the same for other EU countries.
The 'within the EU' limits are so high you can not take them into the plane.