Pour the ginger syrup, orange juice, cranberry juice and vodka into a pitcher. Stir in the grenadine, if desired.
Add fresh cranberries and orange slices for garnish. Place in fridge until chilled and ready to serve.
Fill glass with about 2/3 of the cocktail mixture and top it off with soda*, stir and enjoy!
*If you prefer a sweeter cocktail, diet or regular lemon-lime soda is great in this! However, if you like it a little more tart, club soda works great. If you're a ginger-lover and want an extra boost of it, ginger beer would be a fun way to top it off, too!**If you can't find ginger simple syrup or wish to make your own, here's how: In a small saucepan, stir together 1 c water, 1 c sugar and 1/2 c fresh, peeled and coarsely chopped ginger. Cook on medium heat and bring to a boil, stirring occasionally. Once it's reached a boil, let simmer on low for 10 minutes, then remove the ginger pieces and let the liquid cool.