IN THE ALARM CLOCK DIALOGUE TORIEL REVEALS THAT ASRIEL USED TO FILL GLASSES UP TO THE BRIM BECAUSE HE KNEW SOMEONE ELSE WHO DID SO
AND IT'S HEAVILY IMPLIED THAT THAT SOMEONE ELSE IS CHARA
AND EVEN AFTER CHARA'S DEATH, FLOWEY AND TORIEL STILL FILL GLASSES UP TO THE BRIM AND ASGORE MENTIONS THAT IT'S MORE EFFICIENT THAT WAY WHICH IS EXACTLY WHAT CHARA USED TO SAY ABOUT IT