An odor from your tap is commonly from the sink drain and not the water. The plumbing beneath your sink, typically the u-shape pipe, can collect debris over time and create an odor at your tap. If you smell an odor, fill a clean glass halfway with tap water and smell the water in a separate room or outdoors. If the odor is no longer present, the odor is likely from the plumbing beneath your sink. If the smell is still present it may be your hot water heater.
Single handle water faucets are typically being used in these situations and are not being fully turned on the cold position. This can occur when a water heater is too large for amount of hot water typically used or may be stale water. This happens in homes that are left vacant for a long period of time. Flush lines to bring in fresh water and total chlorine residual. Heating the water can liberate hydrogen. If there are any sulfur compounds available, the result would be the formation of Hydrogen Sulfide, a rotten egg odor causing gas.