It's easy to imagine what you'd buy for yourself if you were a millionaire. When you talk to actual millionaires, though, you realize that no one makes a million dollars — or keeps it — by spending indiscriminately.

Make It has spoken with plenty of millionaires over the years and often asks them, "What do you refuse to spend money on?" The answers show that even when you ostensibly have funds to spare, it's important to be intentional about your spending if you hope to grow and preserve your wealth.

For some, like millionaire Todd Baldwin, frugality is something almost akin to a game. "It's actually really fun being able to buy something and then choosing not to," he previously told CNBC Make It.

Here's what he and four other self-made millionaires say they never spend money on.

Fast fashion

Jonathan Sanchez, a self-made millionaire and founder of Parent Portfolio, maintains a low clothing budget by keeping things straightforward.

"I don't overthink my outfits. I keep a small closet of simple, timeless clothes," he says. "If I'm going casual, I'll pair blue jeans with a T-shirt or polo. If I'm attending a formal event, I'll wear a suit and tie."

This convention allows him to avoid the temptation of spending on flashy new outfits or cheap, disposable fashions.

"I only buy new items when I need to replace clothes with unforgiving holes from normal wear and tear."

Extended warranties

Steve Adcock publishes his Millionaire Habits newsletter as part of an effort to lead people to financial independence and early retirement the way he got there — by succeeding professionally, investing wisely and living frugally.

One thing you'll never see him spend on: extended warranties on household appliances and electronics from big-box stores.

 "You're probably not going to use it. It's just additional profit for the store," he says.

Instead of springing for the warranty, Adcock puts a little cash into his emergency fund each month to cover repairs. When an item breaks, he has the funds to cover it. If it lasts forever, he can put the money toward other expenses.

Pricey alcohol

CNBC's own Jim Cramer says he was raised by the type of frugal parents who wouldn't let the kids order sodas at a restaurant until the food came to avoid a charge for the refill.

As an adult, Cramer takes a similarly thrifty approach when it comes to adult beverages — an expense on something that simply won't last.

"When I see a bottle of wine that's for $500, I say, 'What a waste,'" he says. "Why don't you just go buy a beautiful sweater? Can you imagine the kind of sweater you can get for that? $500? You could get two great cashmere sweaters."

Athleisure

Why spend on something expensive when something free will work just as well? That's Crush Your Money Goals founder Bernadette Joy's thinking when it comes to workout clothes.

"Thanks to the rise of the athleisure industry, sometimes going to the gym feels more like a fashion show than a fitness routine," she says. "Since I go to several conferences and events a year that offer swag, I will gladly wear those free T-shirts to my yoga dance classes instead of spending money on designer workout clothes."

Nights out with friends

Forget getting things for free — why spend on an activity that can generate income for you? Baldwin says he rarely ever spends on trips to restaurants or to the movies, "but only because I know how to get paid for that."

Baldwin is a "secret shopper" and gets paid for dining out, going grocery shopping, seeing movies and even visiting hotels and casinos, in exchange for offering feedback on the products and services he uses.

"If a buddy wants to go to a bar or someone wants to go see a movie, I usually try to wait until I can get a mystery shop," he says, "because if you're going to go there anyway, you might as well get it for free and get paid on the top."

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