There is no clear scientific evidence that taking probiotic pills or eating yoghurt can treat yeast infections in any part of the body or are effective in maintaining a "healthy gut", however that is defined. I am not aware of any evidence for the effect of probiotics on BG levels. I am not sure by what mechanism probiotics would do this. If somebody claims that probiotics has an effect on BG levels, I would like to ask them what kind of evidence they have to support the claim.