I'm no expert, but I understand apple cider vinegar has a lot of health benefits that white vinegar lacks.
You could try making your own? It does take a while though. How to Make Apple Cider Vinegar with the Mother from Scraps (not sure how your tropical climate would affect this. It might be quicker)
We just had a litter of 11 (8 alive) purebred rexes from a first time mum. Both buck and doe had been given small amounts of ACV in their water for about 2 weeks before we bred them. Definitely give this a try!!
you just want unfiltered vinegar mostly, with the floaties (aka live bacteria, aka mother) still in it. Some feel it is the probiotic effect, some think the acid helps, me, I think they like it and drink more water. Water is always good for you.
You are in a hot area, right? how hot has it been there for the last month? I am wondering if the buck gets temporarily sterile from the heat. this is a thing, some one in the tropics (@hotzcatz ?) may have tips.