Fill a cocktail shaker with ice. Pour in orange juice and Tequila. Shake for 20 seconds.
Fill a highball glass with ice and strain the tequila mixer into the glass.
Pour the grenadine over the back of a spoon held over the top of the glass. This guides the grenadine syrup down the side of the glass. It will sink to the bottom of the glass creating a red layer at the bottom.
Do not stir the drink. Garnish with an orange wheel and 1 or 2 maraschino cherries. You can skewer the cherries on a cocktail toothpick or just add them on top of the ice.
Right before serving, very gently and slowly, stir one turn from the bottom of the drink to create the sunrise effect.
A Collins glass is taller and more narrow, but often used interchangeably with the highball glass.