The 44-year-old former baseball star was undecided what to get for the singer and he eventually settled on splashing out on the $140,000 red 2019 Porsche 911 GTS.
In a YouTube video, he said: ''There's a lot of pressure because it's Jennifer's birthday coming up on July 24, and we've been thinking about what do we get Jennifer for her birthday. What do you get someone who already has everything? You have to be creative. We've been talking about maybe a car. The irony is we're gonna buy her a car but she hasn't driven in 25 years.''
And Jennifer was incredibly surprised when she saw the car on their drive.
She said: ''What the hell?! What is that? Oh my god, I'm gonna have to drive? I've never driven a car like that ... I've never driven a car, period.''
Meanwhile, Alex recently branded Jennifer as a superhero.
He said: ''I've never met anyone who's more honest. She's so authentic and genuine. It was strange to see someone of such magnitude be so normal, be such a great mother and partner and friend. How can you be like this and then go perform in front of 80,000 people? But that's her superpower.''
And Jennifer had confessed she was ''wary'' of the idea of marrying Alex after having already gone through three divorces but when he got down on one knee, it just felt right.
She said: ''I was very wary after everything I've been through. I was just sussing it out until then. I was like, 'I don't know, maybe yes, maybe no, I really love [Alex], I like him.' Everything seemed almost too perfect too soon, so I was like, 'Wait, what's happening?' When it happened, I think it was the right time - we knew. It's great to have a best friend and a partner you can really build with, and I just feel like, with Alex and I, that's what it's like. We're very similar ... it's one of those things, you meet a like-minded person who is trying to be the best person they can be and always trying to grow, and then they help you grow and you help them grow. I'm better here, he's better there and we're better together.''
What's new in the music world this week?
LCD Soundsystem was released on this day (January 24) in 2005.
Watch three incredible live performances from Discovr.TV.
Don't miss the K-pop titans' return to Europe.
Listen to Alex Bayly performing 'Animal'.
Two weeks ahead of Independent Venue Week, Dry Cleaning made 'Britain's Best Small Venue 2015' (NME) the second port of call on their 2020 tour.