Originally Posted by UniChris

You can, but it's probably simpler if you make it in bottle or week size batches. A whole tub of the premade powder tends to get clumpy once opened.

A while back I picked up a cheap little .01 gram scale, I'd probably find some light plastic pan (or even fold one from paper) and tare the scale with that, weigh out the salts first, and then do the sugars there for a small batch, or with measuring cups for a larger one.

Remember to take into account the difference between the weight of potassium vs potassium chloride, same for sodium. Or you can look up the amount in volume measures like a teaspoon/tablespoon. I'd be tempted to keep it in a wire-latch mason jar (hmm, might actually go get one and transfer my tub of gatorade to it).