Rinse the strawberries and drain them thoroughly. Slice off the tops and any hard tips, then halve the smaller berries and quarter the larger ones. Place all the berries in a plastic bowl with a right-fitting lid.
Pour the sugar free raspberry syrup over the strawberries, tightly cover the bowl with the lid, and gently shake it to coat all the berries with syrup.
Store in the refrigerator until it’s time to serve the berries, shaking and turning occasionally to keep the strawberries moist and marinating.