In general you need vinegar to be safe. the vinegar inhibits botulism from growing. However, many of us use all vinegar and no water for safety. To me adding water just increases the chances of something going wrong.

You can use just water, but you MUST use a pressure cooker to kill anything that might be growing in the peppers. If vinegar, then a water bath is good enough.

Also, cherry peppers are thick and will hold air if you don't pull the stem off and cut a hole in the top. We halve ours to be sure and water-bath in red wine vinegar, no water. The leftover vinegar is great in marinades and vinaigrettes, bloody mary mix, etc. A few jars had garlic and fresh oregano and basil added.
brookthecook

I just did my first batch and followed a set of detailed instructions online - it called for 5 cups apple cider vinegar and 1 cup water.

Also - I jarred them whole and just cut a slit in the bottoms....

How will I know if they are good to eat when I open them? Smell? All this talk of botulism and other stuff is discouraging me and makes me feel like its not worth the risk. Ugh....

I use 100% vinegar (5% acidity) some peppercorns, salt, a few garlic cloves. And that is it. Always works great. Let them sit a couple of weeks before giving in to temptation! I Just jarred my first batch tonight!