Storage: double-strength coffee keeps in a sealed jar in the fridge for up to a week; classic syrup keeps for two to three weeks — shake it if the sugar settles. Freeze leftover brewed coffee as ice cubes so your drink never waters down. For dairy-free, oat milk is the closest match. If you only have dark roast, add a little extra syrup. Decaf works but brew 5 tablespoons for the same 2 cups of water.