they are very similar but have some differences. here is a section about the differences from Yemoos.com
Ginger Beer vs Water Kefir
Both are symbiotic colonies of bacteria and yeast and perform similar
functions of fermenting sugary-water, but that is about where the similarities
end. Just...
Just some info for anyone thinking about trying this. There is no federal or any other regulation on selling GBP and many sites individuals out there are less than honest about their GBP. Many sell plain yeast, water Kefir grains or in the case of retro-culture.com a hybrid of water kefir...