One jar is good.
Two is better.
These mason jars are on the largish side, the more, the better. This is a recipe that luckily really can't go wrong. It goes like this:
1 bottle of decent vodka OR Bombay Sapphire gin
app. 200 grams sugar (I use organic cane sugar)
Place the above ingredients in a large jar. Fill the remaining space up with diced rhubarb.
Shake daily for 4-6 weeks, keep in a cool, dark spot.
Enjoy straight up.