My kids are SOOOOO clumsy, so I feel your pain with the cups at dinner. I actually started filling their cups only halfway, and having a towel nearby. I also teach them to keep their cup on the other side of their plate to prevent elbows from causing spills. They also used to be told to use two hands. Another thing I started doing, which honestly became the turning point for us, is I started making them clean up their own spills. They used to spill a drink every single day. BUT, after I started saying "get a towel and clean it up" and then checking to see if they got it all, the spills became fewer and fewer! Now, they're 6 and 7, and we only have spills maybe every couple of weeks or so. It's amazing what personal responsibility can fix when you make them do the cleanups!!