Adding cold brew to an Old Fashioned: control concentration first

The source adapts an Old Fashioned by adding cold-brew coffee to bourbon, sugar and bitters. Its practical reason for choosing concentrate is that coffee flavor can be added with less liquid than a weaker brewed cup. That is a recipe-design choice, not evidence that every cold brew will combine equally well with every spirit.

Begin with a measured small serving and keep track of the coffee concentration as well as its volume. Dissolve the chosen sugar appropriately, combine the components and add ice with room to stir. The source discusses brown sugar and simple syrup as alternatives; their equal spoonfuls need not contribute identical sweetness or water. A prepared syrup also changes the dilution calculation.

Taste the coffee independently before mixing so you know whether its bitterness, roast character or fruit acidity suits the intended cocktail. Keep later changes to one component at a time. This is an overview of the source's alcoholic coffee-drink variation, not a complete standard cocktail specification where the extracted article omits quantities. No therapeutic or performance benefit is implied by combining coffee and alcohol.