You can use traditional clay cups called Jarritos de Barro or if you don't have those just use a highball glass.
Two types of Clay Cups (Jarritos de Barro)-UNGLAZED cups will need to be soaked in ice water for about 10-15 minutes before you drink from them. This has two purposes; to chill the glass for a really nice cold drink, and to saturate the clay so it doesn't absorb your cocktail. You will also want to make sure you don't use soap on these cups, they are meant to only be rinsed with water.GLAZED cups are raw clay on the outside and glazed on the inside so your drink won't soak into the cup. These can also be soaked in ice water but it isn't totally necessary. They are also generally dishwasher safe. (this is the type I use)
TIP: if you are going to soak your cups do it while you squeeze all your fresh juices!
Fill your cup half way with ice. Set aside.
In your cocktail shaker add a few cubes of ice, tequila, a pinch of kosher salt, fresh squeezed grapefruit, orange and lime juices.
Pop the lid on the shaker and give it a vigorous shake for about 20 seconds.
Strain into your drinking glass/cup. Top with 2 oz of grapefruit soda.
Optionally garnish with a lime, grapefruit or orange wedge.
Tequila: a silver or tequila blanco works best in this Mexican cocktail. I like Jose Cuervo Traditional ($), Espolon ($$), Cazadores ($$), or Casa Migos ($$$).Grapefruit Soda: There are a few options for the soda added. You can grab any of these brands: Jarritos, Squirt, Fever Tree, or Q Mixers. Use Fresca for less sugar but it will change the flavor of the drink.