Cynthia Erivo doesn't "eat anything on planes" because she wants to preserve her voice

Cynthia, 38, told The Hollywood Reporter: "I'm always taking care of it.

"I don't drink. I don't smoke. I'm a crazy person. I don't eat anything on planes. I bring everything with me: my tea, my water. Someone made a meme of the mug that I carry around because I have it with me everywhere. I have it in several different colours. I will not be without it because I want my tea to always be warm enough to hydrate me.

"That's just how I exist. I will do whatever I need to make sure she's okay - except apparently take a break."

Meanwhile, Cynthia recently revealed that she "made a pact" with Ariana Grande before shooting the Wicked movies.

In her book, entitled Simply More: A Book for Anyone Who Has Been Told They're Too Much, Cynthia explained: "Before Wicked really started rolling, Ariana and I made a pact with each other.

"We committed to protecting and caring for each other through this process. We hear often how female costars -¬ or really, any costars -¬ can sometimes let their egos get in the way until they battle each other, destroying the creative process for everyone involved. We were determined to do the opposite."

Cynthia believes she shares a "strong synergy" with her co-star, who has become a close friend in recent years.

The London-born actress - who also stars alongside Jonathan Bailey in the money-spinning film franchise - said: 'We were always looking out for each other. Our partnership was important. We shared a strong synergy, a commitment to authenticity, and that, combined with the natural connection we fostered both on and off set, allowed us to support each other emotionally and professionally."