Well, virtually anything but Turkish Lira.

I keep dollars and crypto. Real estate isn't a bad option either. Basically anything that's not practically pegged to TL is a good choice in my opinion. And this includes almost anything: foreign currencies, crypto, real estate, cars, gold, stocks (foreign) etc.

If you have a house or a place to install them then something like solar panels in Turkey would be a great investment as it generates income (or at least cancels out future expenses )