When I was in the Army, we had a guy who used to tape one under his arm on drug test days.
He'd fill it with his kids urine first. Then run a piece of tubing from the bulb down to his pecker and cap the tubing.
Keeping it under his arm caused it to be warm. When it was his time to pee, he'd uncap the tubing and squeeze the bulb with his arm.
Clean pee.