Freeze sangria and ready-to-serve margarita in separate containers (I used plastic Ziploc/Tupperware tubs).

When frozen, use a fork to scratch it up like a granita since it will not be fully frozen (because of the alcohol).

Spoon into glasses with alternating colors.

Drizzle grenadine over the sangria part to improve the red color and to add a little sweetness and moisture (the drink will be very icy).

Serve with small straws and garnishes of your choice. You can also choose to rim the glass with sugar (I did not).