i think what a big part of people are asking for with 'sand throwing' is just basic codified martial combat actions beyond 'hit it' and then for the fighter to have a better ability to use those actions because they're meant to be this 'skilled martial warrior' but they're a SkIlLeD mArTiAl WaRrIoR who can only really hit things with their fancy metal sticks, the ability to trip, blind, disarm, parry, shove, taunt, daze, distract, deafean, slow an enemy's movement, focus themselves, called shots to disable an arm, feint and more all those things would be great for any character to be able to perform with their action but the fighter, as a skilled warrior the fighter can sub in any one of those for one of their attacks without missing a beat, almost like rogue's cunning action but for martial fightery things instead.
and it's not about explicitly being able to 'throw sand' to blind someone, you could be attacking their eyes, reflecting light into them, pulling down their helmet or flipping their cloak over their head, any number of things but it's not something that has a codified method of attempting it in a fight and it should be, because near all those things i mentioned in the paragraph above even you or i could do to someone in a fight, and this is THE FIGHTER we're talking about.
unrelated: this is only just my own personal want but i'd love if the fighter had some sort of 'boot camp crash course' ability, where over the duration of a short/long rest they could train or get trained by another character to have temporary proficiency in a skill the trainer has for 4/12 hours