Set up a hurdle low enough to hop over and stand to the side of it. Hop over the hurdle using both feet, being careful not to trip. Hop back over to work the opposite side.
The hurdle can be as low as a line marked on the ground, to as high as your jumping abilities will allow. Try one-legged hops, or hops with a 180 or 360 degree spin for an advanced challenge.
If you have multiple hurdles, you can set them up in a row in order to challenge your endurance hopping multiple times in one direction. You can also hop laterally forwards or backwards over multiple hurdles to trace a diagonal line or zig zag pattern.