Do sand snakes eat snakes

Answer 1

'Sand snake' is not a common name for any snake I am aware of (except in 'Star Wars' novels where a Sand Snake is a fur covered snake native to Geonosis.)

You may be referring to a 'Sand Boa'. In which case, it would be very unusual for them to eat another snake, but like with most snakes, anything that can fit in its mouth may be considered food under the right conditions (such as if its standard diet is not available for prolonged periods, or if two grab the same food item, the larger will keep eating and eat the smaller snake).