Is it spongy after the pads contact the disc, or is it just a lot of dead travel before contact?
If it’s the latter, it sounds like the pistons aren’t advancing properly. Try applying the brakes repeatedly and firmly, or try the trick of tying the lever back to the bar leave it.
If it’s spongy then you’ve still got air in it.
When did it start feeling spongy – was it in use or after storage? Unless you’ve got a leak in your brakes, they won’t suddenly take on air and need a bleed. What can happen is that if you store it on a wall or upside down, air that was sitting harmlessly in the reservoir at the top can make it into the brake lines. Repeatedly applying or flicking the brakes usually sorts it pretty quickly.