Is it safe to soak feet in vinegar everyday for toe fungus?

I don't. believe there is any side effect of doing so. YOur assuming the vinegar will treat the fungus though. I am not sure there is evidence based medicine proving that.
Vinegar, no oil.... Soaking in a mild vinegar solution has been shown to alter the acid/base environment that most fungus thrive in. So in many cases, it appears to have a healing effect. The skin is the most responsive so when used in conjunction with topical anti fungal creams, even the most stubborn fungus infections can be treated successfully. Sorry to say though, the results are not as rosy for nail treatment.