Put water, sugar, and toffee pieces in a medium saucepan and bring to a boil.
Lower heat and let simmer for about 10 minutes, until syrup has thickened a bit.
Strain syrup into a bowl, leaving any remaining toffee pieces behind.
Keep syrup in bowl or pour into a mason jar and place in fridge to cool completely before using.
Store syrup in an airtight container in the fridge for about a month.