Here is a picture of the best jar I've found for brewing Water Kefir. I found it at Walmart for about $5.
It's being brewed with ½ cup sugar, ¼ cup crystals, 3 liters water and 2 "quarters" of Ginger. It has been brewing for 24 hours and is ready to drink.
(I let it brew for another 24 hours though because I prefer my Water Kefir not quite so sweet.)

This is a close-up of the lid for the best jar I've found for brewing Water Kefir.
The rubber seal is snug against the glass lid, making it difficult to twist, but not impossible.
This lid creates a very nice seal. It prevents undesirable bacteria from entering the brew, yet allows excess carbon dioxide (bubbles) to escape. The finished beverage is noticeably carbonated, but not nearly as much as a soda pop.
