From TCM theory, it might be the cold and wind that is causing the intestinal contractions, then the pain. If the belly is cold to the touch, feeling hard and stiff, then try this home remedy that costs only a few dollars: make a cloth pouch large enough, or just an old T-shirt, to wrap up up to a pound of large grain rock salt or sea salt.
Pan fry (the traditional way) the loose salt grains, or microwave the pouch/T-shirt pack to a bearable temperature, lay it flat on the belly button area. Moving it around for an even warm up. Reheat and reuse. If heating helps, when leaving home for work, or at bedtime, apply a bean size Capsaicin Cream 0.025% into the inside of the belly button, use a bandaid to cover it. The heat would last for many hours. It also helps with pains too.
Rubbing the belly area with a full palm in a circular motion with hard presses, not just slide across the skin, keep changing directions might help with gas, bloating and bowels. As for the occasional sharp pain, I cannot think of any cause to it except, just a big speculation, he might have worms.
Hope it helps a bit. Best of luck to your friend.