The cups you refer to are a little too small even for newborns. Your snakes are probably 6 to 7 inches long and the container only 6 inches. I personally prefer the "shoe box" size containers (12 inches long x 6 inched wide x 4 inches high). These are reasonably cheap $1 to 2 USD, with locking lids. As they grow you'll eventually need to move them to someting larger. I keep 3 or 4 per container.

Sid