Water, sand, and… what else? Let’s test each other’s understanding of the basics.
I’d go with “chemical additives” — mainly a slickwater friction reducer (polyacrylamide), with a bit of biocide. Tiny caveat: sand’s the proppant, not really a fluid, but it rides the slurry like a passenger on a crowded bus. Do you want to count the HCl preflush in the top three?