Splash equivalent

If a recipe calls for a splash of something, say club soda, and you want to batch it up to say 5 or 10 times the specified recipe for a party punch, what is the best unit of measure to use to keep consistency without physically pouring 5 or 10 individual splashes? I know not all splashes are created equal but would you say it's around a half an oz? More? Less?

A quarter ounce, though I would imagine you wouldn't want a batch of anything using club soda unless you were serving it to everyone at once.