Cider vinegar in water is what I'd use. In fact, I don't care for how lemon can interfere with the apple taste and other flavors, so I often use cider vinegar even if I have lemons on hand. And I've never found it necessary to add more sugar. But that's just me . . . .;o)

Why would it matter if they're going in a pie? For the record, Cortlands don't get brown quickly.

Oh--I agree with savorykitchen--i never use commercial anti-browning agents either.

I never use any anti-browning agents - my apples may tan up a bit, but it's never unappealing. If you're really concerned, a splash of cider vinegar (maybe with a little more sugar to counteract) could work.

If you're using Granny Smith or other very tart apples, it's probably not a problem. I would get everything together before starting to peel and slice the apples, then add the apple slices to your sugar/spice/flour mixture as soon as you slice each one and toss it well. Work quickly and you'll probably be OK.