Most store-bought, commercially produced grenadine syrup is nothing more than dayglow-red corn syrup. Real grenadine is easy to make, stores easily, and actually adds character to cocktails.
16 oz pomegranate juice
2-4 cups of sugar (dependent on your desired thickness)
Squeeze of fresh lemon juice
2-3 dashes orange blossom water
Heat pomegranate juice in a non-reactive pan over medium heat until barely simmering. Add sugar– a 1:1 ratio will produce a thin grenadine, and a 2:1 ratio will produce a thick syrupy consistency. Stir until sugar is fully dissolved. Bring liquid back to a simmer, reduce heat, and maintain the simmer for 5 minutes. Do not boil.
Remove from heat, let cool for 10 minutes. Add lemon juice and orange blossom water. Let cool fully and store in fridge in a closed sterilized glass vessel. The grenadine will last 2-4 weeks in the fridge–longer depending on sugar content.
Find it online: https://food.ryanbladzik.com/drinks-infusions/grenadine-syrup/