If you mean you want to drink the wash from the cup after you've used it to wash your eye then I'd say no, I would not drink it.
If you mean you want to use it to wash the other eye instead of preparing another batch, there are people here who prepare one eyecup and wash both eyes with the same wash. That is a matter of personal preference, unless of course you've got parasites in your eyes, if so you do not want to use the same cup for both eyes.
The directions are to take 2-4 droppersuful internally each time you do an eyewash so 10 drops of the Eyebright in an ounce of water isn't that much to throw away.
And let me just say WHOA......you are the only person I've heard about other than hearing Dr. Schulze talk about it that is actually using 10 drops in the eyecup! If I haven't misunderstood what you're saying, good for you!!!!! ;)) I do believe we'll have to give you the award for using the most drops!