Step back from ideas like "he's not applying himself" - that's the kind of language schools use to make kids feel bad about the fact that they don't dovetail conveniently with a particular educational method. Kids don't fail at school from not applying themselves, schools fail to meet their needs. Tell him that - it will help his self-esteem.
That being said, math is everywhere, all the time. Schools mostly ruin it for people, so the best thing you can do is offer fun things that don't "look" like math.
Video games are a great example - they're pretty solidly math, certainly a much better way for kids to internalize the concepts.
Art is a math-rich endeavor, if he's artistic. Music, obviously, but all kinds of art depend on an intuitive grasp of mathematical principles.
Any kind of goopy, messy activity involves and exploration of chemical properties, and therefore math. Making "potions," making mud, cooking and baking.
Playing with flight involves a ton of intuitive math - airplanes, frisbees, balls, rockets, zip lines, parachutes, balloons. And things with wheels depend on a lot of the same concepts - bicycles, scooters, skates, skateboards, toy cars. Ramps and jumps and loops. Bunny hops and ollies.
All the juggling arts are enormously rich in physics, and therefore math: balls, clubs, poi, devil sticks, contact juggling, diablos. Yoyos. Hula hoops.
Magnets and electricity are good fun, full of math, and make easy gifts. Snap circuits. Things with motors. Magnetic toys and kits. Compass experiments.
Building toys of all kinds are great for playing with mathematical principles. Legos and lego-compatible K'nex are fantastic, but for added fun there are also marble runs, race-car tracks, kits with wheels, gears and pulleys, simple robot kits.
The main thing is to recognize that learning about patterns, connections, and interactions - real world math - isn't going to look anything like school math. And that's a good thing because schools ruin "math" for most people. Really playing with math often involves separating the idea of "math" from actual math so that you don't get bogged down in school damage and can actually learn something interesting.