Alex played 80 minutes, earning his fourth Under-21 cap, as Jim Crawford's side slipped to a disappointing defeat at the hands of their Danish counterparts.
Emil Frederiksen scored the only goal on the half-hour as Denmark ran out comfortable winners.
This was Ireland's final game before Euro 2023 qualifying begins with games away in Bosnia-Herzegovina and Luxembourg in early September.
Pontus Jansson wasn't in the matchday squad as Sweden beat Armenia 3-1 in their final warm up game ahead of Euro 2020.
Emil Forsberg's free-kick gave the Swedes the lead in the 16th minute before Marcus Danielson headed in to make it 2-0 ten minutes before the break.
Vahan Bichakhchyan pulled a goal back for the visitors just after the hour mark, but the Swedes netted a third through Marcus Berg late on to make it safe.
Sweden open their campaign against Spain in Seville next Monday, kick-off 8pm.