Which will result in a reduction of alcohol in a person’s bloodstream and help them sober up?

Only passage of time will result in a reduction of alcohol in a person's bloodstream and help them sober up.
The liver is responsible for metabolizing alcohol, and it can only process a certain amount of alcohol each hour. There is no way to speed up this process.
Drinking coffee, exercising vigorously, and taking a cold shower may make a person feel more alert, but they will not reduce the amount of alcohol in their bloodstream.
In fact, exercising vigorously can actually increase the absorption of alcohol into the bloodstream.