Sometimes a sewage or stagnant-type odour can come from a sink/plug hole. This usually means there has been a blockage or build up of waste materials, which makes the drinking water appear to smell.
Filling a glass with water and smelling it in a different room, away from the kitchen sink, will help you work out whether the odour is genuinely from the water or not. If you think it is the water please contact your water supplier immediately.
If the odour disappears when you're away from the sink you should try cleaning your sink/plug hole with a normal domestic cleaner. However, if there has been recent work on your service pipe, or you have had a new connection to your property, it could indicate a problem with this work and you should contact your water supplier immediately.