Paul Rudd has said that his diet while preparing to play Ant-Man was so restrictive, that he drank sparkling water as a reward.

"When I was having to train for the 'Ant-Man' movie, I was on a very restrictive diet. My reward was sparkling water," Rudd said on Wednesday's episode of the Off Menu podcast. In the show, guests are asked to recall their multi-course “dream menu” by hosts Ed Gamble and James Acaster.

"That's how horrible that diet was. I was like, 'Ugh alright. I'm going to have some sparkling water now. I've earned it,'" continued the actor.

Rudd said that his favourite sparkling water brand is San Pellegrino, and that it wasn't difficult acclimating to the diet because he is okay with eating bland food.

“Did it feel like a treat?” Acaster asked, with Rudd replying: “Yeah, it was great. It wasn’t flavoured, I wasn’t gonna go crazy.” He added that he “kind of did it” for all the Marvel films and that it was sometimes easier than expected.

Rudd isn’t the only actor to open up about undergoing intense training and diet for a role, as Scarlett Johansson, Jeremy Allen White, Robert Pattinson and Channing Tatum are among others who have previously shared their experiences in Hollywood.

The Only Murders in The Building actor also recalled, "I remember on Endgame, Chris Hemsworth would always have these Tupperware containers and he’s eating this gruel of just a mash of stuff. He’s working out, and then you stand next to a guy like that, and I just think, ‘Well, what’s the point of any of this?’ Why am I killing myself when that can exist, then I look at myself and this exists. I can never achieve that. …That was the good thing that it was Ant-Man, it isn’t Thor. But I tried to work out, and it didn’t work."

Paul Rudd joined the Marvel Cinematic Universe in 2015, most recently starring in Ant-Man and the Wasp: Quantumania earlier this year.