(are you in town for Worldcon?)
The storehouse is one of the highest-rated tourist attractions in Europe. I’ve not done it in ages, but it’s really interesting and there are multiple bars inside. Plus you get the chance to pull your own pint.
If you do the storehouse there are a few other points of interest nearby that you’d be able to do in a day - the Jameson visitor centre in Smithfield Square, on the site of their original distillery, the Irish Museum of Modern Art in the Royal Hospital Kilmanham (most of the galleries are free to view, but there is often a travelling exhibition that you need to pay to see), and Kilmanham Gaol, which is a museum to the 1916 rising and War of Independence (and was restored by my great-grandfather, amongst others)
