Size of Reviit

What is the smallest number of ounces that qualifies as a reviit?

What is your specific scenario that you are asking in reference to?

There is an old halachic debate about the correct sizes. The Rav has always told us that we need 5.3 oz for kiddush and havdallah or to make a borie nefashot on a drink.

For health reasons I minimize sugar intake. A sip of grape juice for Kiddush is not a problem. However, the amount of sugar in the four cups at Pesach is a lot of sugar, even with drinking just over half of each cup. I am trying to determine the least amount that I can drink and still keep the mitzvah. If I do strait wine or mix them, the sugar load is down but so am I.

The cup should hold 5.3 oz.

One should drink the majority of the cup. Drinking the entire cup is even better.

If it’s difficult for one to drink this much they can drink 1.7 oz (the cup should hold 5.3 oz).

Why not use a very dry wine? That is what I do.