The size of the ginger is up to you it depends on how intense or mild you like the ginger flavor. I love it, so go big. Peel the ginger and lightly hit it on the cutting board with a heavy pan or mallet just enough to release the juices.
In a small sauce pot add the water, honey and ginger. Boil until reduced by half and has thickened slightly. Remove the ginger. Pour syrup into a ball jar and let cool. This can be made ahead and stored in the fridge for up to 2 weeks.
Juice the 2 limes and 1 grapefruit. You should have about 1 cup of juice. Fill a cocktail shaker half way with ice. Add tequila, fruit juices, water and syrup shake until very cold.
Fill two glasses with crushed ice and sliced strawberries. Pour cocktail over ice and enjoy!
This is also amazing with sliced peaches or other stone fruits substituted for the strawberries.