Yeah I know what ketosis means. It means more stomach acid.
At least the water will help flush it out.
Hence the acidy breath (bleurgh) x
Er... no. It doesn't, actually. There'll be ketones in your breath - the whiff doesn't come from stomach acid.
In the absence of carbs, the liver breaks down fat to release its energy to power gluconeogenesis (the conversion of protein to sugar) and produces ketones as a byproduct.
Ketones are basically water soluble (meaning they dissolve in blood) fats that are a source of energy for many tissues including the muscles, brain and heart. In fact, ketones act as a stand in for sugar in the brain. Although ketones can’t totally replace all the sugar required by the brain, they can replace a pretty good chunk of it. And ketones are the preferred fuel for the heart, making that organ operate at about 28 percent greater efficiency.
Fat is the perfect fuel. Part of it provides energy to the liver so that the liver can convert protein to glucose. The unusable part of the fat then converts to ketones, which reduce the need for glucose and spares your muscle mass in the process.
Because initially your body produces more ketones than it can use, the body needs to get rid of them. Some spill over into your urine, some are excreted via your breath, making your breath whiffy.
Ketones in the breath smell like acetone, often described as peardrops or the smell of overripe apples.
The other reason for bad breath is that ketosis causes a degree of dehydration, so you don't produce as much saliva, leading to an increase in the population of bacteria in your mouth which in turn causes bad breath.
That's one of the reasons why it's important to drink plenty (at least 4 pints of water a day, more if you're having tetras or bars) - it has a double whammy effect of decreasing the concentration of ketones in your breath and urine (so neither smell as strong) and increasing the saliva in your mouth.