We have a huge fantastic Mediterranean market with 5 kinds of feta and at least 8 kinds of olives in their deli area. (Also the most decadent homemade full-fat Greek yogurt you've ever tasted.) But neither the feta nor olives come in their own storage liquid. And it saddens me to toss out feta that's started to mold or olives because I'm not sure I should trust them. I went looking for solutions. These work:
Feta:
1 T salt
1 cup water
Make enough to completely submerge your feta in some tupperware. It may come out a little dryer/saltier than it went in, but it will NOT come out with a new stinky microbiome :-)
Olives:
1.5 T salt
1 c water
1/4 c red wine vinegar
Dissolve salt in water and add vinegar.