it will most certainly be a drainage problem identified by the putrid smell which is emanating from the sewers up to the drainage pipe under your sink . I have had this problem exactly as you describe as intermittent .It is caused by the menace of leaves in autumn blocking the drain filter ring that sits on the drain hole that leads the waste from all three sources of waste water to the sewer located outside your property on a pathway at the side of your house .The three waste pipes are from the kitchen sink , the the bath water , and the bathroom sink unit . The cure is to lift the ring and keep broddelling the sump till the standing water in it drains away , then run the cold water at full bore from your kitchen sink to check that the water runs away and does not fill up the sump to overflow back up beyond the level of where the ring sits . There after , boil a kettle full of water to pour it down the drain plug with a bit of washing up liquid . But better still is to use "Sink & Drain Unblocker" from HomeBase costing 99p to pour down the kitchen sink overnight .