Lemon juice works better on blonde and light colored hair. Apple cider vinegar, balsamic vinegar, (and red wine vinegars for more of a reddish tint, especially good on people who have some red to their hair) works better on brunettes (lemon tends to make brunettes more orangey than 'caramel').
After you're done with sun-streaking or even just using a blow dryer, take a shower and wash/rinse your hair. Lemon juice (dried) will make your hair feel tacky with the sugars and apple cider vinegar sprayed straight may feel oily after awhile.
Also, you can try adding a pinch of baking soda in your hand and mix it with your regular shampoo. This will get rid of any buildup and minerals in your hair that may be altering the color of your hair and making it mousey.
I've been doing no-poo (baking soda and apple cider vinegar) and my hair has lightened a bit naturally somewhat since I still blow dry my hair before leaving the house.