I Broke My Roommate's Favorite Item by Accident

Last week, my roommate lent me his favorite coffee mug. He had a sentimental attachment to it since he got it as a gift from his grandmother when she passed away last year. I was in such a rush leaving for class that morning and didn't properly hand-wash the mug like I should have; instead, I accidentally dropped it into the sink full of water and let it slip through my fingers when reaching to grab it back up. The whole thing shattered right there on the kitchen floor. I felt sick with guilt after seeing the pieces everywhere, I could tell he was going to be upset. I've been trying to think of a way to make it up to him, but nothing seems like enough. It's not every day someone loses something so meaningful and irreplaceable.