Every summer, people with dark hair who are too non-committal to actually splurge on some recreational balayage Google “How to lighten hair naturally,” squeeze a lemon into a squirt bottle, douse their hair, and sit in the sun for as long as they can stand (we find) to very little in the way of results. Where are the natural highlights of our youth? Surely, they must be attainable without foils.
Word on the street is masking with straight vinegar (or vinegar mixed with lemon) over the course of several months has the potential to lighten hair up to two or three shades. Masking with honey might also do the trick—there's some hydrogen peroxide in the honey that can lightly bleach hair while it oxidizes. Then there are the options you probably don't already have in your pantry.
But really, the point here is to ask you: Have you tried any of this? Does it work? How quickly? Regale us with your blonding stories, friends.