Cleaning a vase is a huge pain in the butt. It’s nearly impossible to scrub the bottom where all the gunk is after your beautiful flowers are long gone. Adding a little uncooked rice to the bottom helps you scrub where you can’t reach.
Before:
After:
I first filled the vase with warm, soapy water and let it sit for a while to loosen up some of the gunk. I dumped half of the water out and poured in a few tablespoons of uncooked rice. It’s a little difficult to swirl the rice around without the water spilling out, so you’ll want to do this over the sink. After a few minutes, I rinsed everything out. There is still a little gunk at the very bottom, but this definitely helped get most of it out.
Source:
Real Simple
Hey, that’s pretty cool! I bet it would work even better with some white vinegar. And then at the end you would have rice vinegar! Really, really gross rice vinegar.
I just put mine in the dishwasher and they come out sparkling.
Can’t stomach the idea of wasting rice! 
That’s really cool! I’ll have to try this out.
I always use denture cleanser tablets, put water in the vase, throw 1-2 tablets in and wash it out after some hours. Helps pretty good, too.