Jon McConnell moved into the quarter-finals after defeating Poland's Damian Durkacz by unanimous decision.
Daina Moorehouse also progressed to the last eight following a split decision victory over Bulgaria's Zlatislava Chukanova.
Moorehouse, who was considered home favourite, had also overcome the same opponent in the Olympic qualifiers for Paris.
Lisa O'Rourke advanced to her quarter-final bout with a unanimous decision win against Greece's Vasiliki Stavridou.
The 2022 World champion dominated the first two rounds before forcing two standing counts in the final round of her last-16 fight.
O'Rourke will now face Team GB's Emily Asquith for a chance to claim a medal at the European Championships.
She is scheduled to meet Italy's Gabriele Guidi Rontani on Monday in the quarter-finals.
The 23-year-old Wicklow fighter claimed a 3-2 victory after taking a count in the final round against Spain's Laura Fuentes Fernandez.
Sweeney was eliminated from the tournament after losing her last-16 bout by a 4-1 margin to Italy's Chiara Mosetti.
She lost the final two rounds of her contest and will not progress beyond the preliminary stage.