You can add variants to your product!
Please select product, scroll down and click Add variants
Tap on + Add another option and select from list:
Size, Color, Material, Custom name
Add your size variants by entering value and tap on +Add
NOTE: You can add only up to 10 values for each option
You also can add Custom variant, for example let's add Water brand name in Custom option. You need to add option title - Water Brand
For adding multiple variant selections, you just need to tap on + Add another option
Here variants will create 6 options: 3 brand names with 2 sizes
Here's how it will look like after the saving options
With this logic you can have up to 3 option and 10 values in each, which gives us 300 variants.
This is how customer will see variant selection:
