The simplest way to deal with a stinky S trap is to just run a bit of water down the pipe to refill the empty trap. You would need to do this every time you drain a full sink, as well as a few times a month in the case of a drain that doesn’t get used too often. However, for a more permanent solution you really should replace the S trap with a properly vented one. Depending on how the plumbing around the fixture is set up, this may be as simple as installing a P trap to replace the S trap. In other cases more extensive work such as adding a vent stack may be required. If you need help with stinky, slow, or unvented drains, an experienced plumbing contractor like US Comfort can help. Call 800-738-4160 to reach us. visit here : https://www.uscomfort.com/plumbing/