The best option for sagging balls is, let them sag. They're doing what they're supposed to do, and "supporting" them only weakens the muscles. Get some knit boxers (the stretchy kind).
Pouch underwear is the wrong answer, especially for "sagging balls". As you soon as you sit down or balls extend, suddenly they are hanging below the pouch and the pouch seam is digging in to you. Pouch underwear is the biggest marketing gimmick that makes absolutely no anatomical sense.
I have very large balls and I have found these offer adequate support while being comfortable at the same time and are a good value. Hopes this answers your question
Fruit of the Loom Men's Breathable Underwear with Tri-Cool Technology - Assorted Color. These support large gonads. The "boys" stay put and dont sweat.
Hi I can understand your husband as I am the same way & it’s uncomfortable when the Balls just slack,
I even tried a jockstrap, wasn’t too bad, I’m going to try these.
You might want to buy your husband these briefs sold here on Amazon: YuKaiChen Men's Pouch Underwear Performance No Ride Up Boxer Briefs. You should check out the pictures of the guy's wearing them!