There have been problems associated with using sand as a substrate for snakes that are not sand/desert dwellers. Based on what I have heard and read, I would recommend against sand.
Suitable options include paper towels, newspaper, aspen or cypress shavings and some bark options.
Pine, Cedar and Redwood shavings should be avoided due to the toxicity of the oils they contain.
I use paper towels for young ones and aspen for adults,
Best Wishes, Skye