Buy a blender bottle, the ones with the small wire ball inside which are designed for mixing protein powders and the like. They're about ~20 floz so fill 8oz with Soylent, 8+ with water and you're good. Throw in some ice, shake, and no chilling is needed.

I stopped using the big container entirely since it's like 3-5$ for a bottle I just bought 2 and always have a clean one.