I wish I had the patience to let something sit in vinegar for 2 weeks. A mixture I have made that worked was ketchup and soy sauce. It worked on a bringing back a date on a penny that looked like it had been buried for 40 years.
Olive oil, vinegar, tomato sauce, ketchup, hot sauce, lemon juice etc etc - all of these things contain a mild acid. That's why they clean coins and sometimes bring the date back. They all do the same thing that Nic-A-Date does, just not as quickly. And any of them treated with any of these things will forever be an altered coin.