You only need 1/4 Cup…

Detergent sheets completely dissolve in the wash.

Single-use? I mean … sure? I guess? The same way a scoop of detergent powder is single-use.

Nobody’s mentioend laundry detergent sheets yet? Super cheap. I buy the Poesie brand. 160 sheets in a box for $9.49. That’s just under 6¢ per load. For my two loads of laundry per week, a box lasts me a year and a half.

Bonus: the box takes up almost no space, 6" x 5" x 3".

Also, white vinegar is an awesome replacement for fabric softener!