Burger King admitted it was "spurred on" by Southampton sisters Ella and Caitlin McEwan's petition against the use of plastic toys in children’s meals.
The fast food chain announced it will remove plastic toys from their children's meals entirely, while McDonalds will allow customers to swap the toys out, in an effort to reduce waste.
The Change.org petition, called on Burger King and McDonald’s to "think of the environment and stop giving plastic toys with their kids’ meals".
The sisters told ITV News McDonalds and Burger King were one of the biggest toy manufacturers in the world, and when they use to get the toys they would never actually play with them.
"They're useless, we don't want them and they're really bad for the environment so let's stop them," 10-year-old Ella McEwan said.
She added: "The environment is in danger, we need to take drastic action because of it and we need to act now.
"You not getting a little plastic toy whenever you go out for some fast food isn't the worst thing in the world."
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While eight-year-old Caitlin McEwan said the plastic "can get to the ocean and the fish and turtles can get stuck in it, or they can accidentally eat it..and that will be bad for them."
In response to the fast food chains ending plastic toys, partly because of their campaign, the sisters expressed their excitement.
Ella said: "I'm just really excited, really happy, and I'm hoping this will provoke other big companies to do something. I'm really hopeful for the future."
Caitlin added: "I'm actually very happy that they listened to us."
Mum, Rachel, said she was really proud of her daughters: "I'm just really amazed at how they've been handling it all, what they are saying is not us telling them what to say.
"They're saying it themselves, and how well they are doing with that and their enthusiasm for it all."
Burger King is removing all plastic toys from its children’s meals served in the UK from Thursday, to save an estimated 320 tonnes of single-use plastics from going into the system annually.
In a separate announcement coinciding with its rival, McDonald’s said it will give customers the option of swapping plastic toys in its Happy Meals for fruit bags or books.
The fast-food chain will begin the option of the fruit bag next month followed by the book from early next year.
Burger King UK Chief Executive Alasdair Murdoch told ITV News: "We have been working on our sustainability strategy for 18 months, but I think it is fair to say Caitlin and Ella did hurry us up along that path, so I think their campaign did draw a light to it and make us more faster."
However the move is only been rolled out in the UK but not worldwide.
"We’re making a start," he added. "This is a step in the right direction.
"If it makes other competitors move their practices forward, that can only be a good thing."
The announcements follow increasing consumer pressure on fast food chains to stop handing out the single-use plastic toys, which parents commonly complain are promptly discarded and only contribute to the waste crisis.
McDonald’s said swapping out the toys, alongside its roll-out of paper straws in restaurants, the removal of McFlurry plastic lids and the removal of single-use plastic from McDonald’s salads, would reduce waste by 1,005 metric tonnes annually.
McDonald’s UK and Ireland chief executive Paul Pomroy said: "We recognise that some people may not want a plastic Happy Meal toy, but we also know that the gifts provide fun for many families and children.
"That’s why we’ll be running these trials, in order to give our customers a choice; they also can choose not to have a toy or gift at all.
"It’s important we understand what our customers want and we’ll learn a lot from whether they choose a fruit bag or a book over a toy."
Burger King is installing amnesty bins in every one of its restaurants across the UK, where people can drop off any free plastic meal toys, including those given away with confectionery or within children’s magazines.
The plastic will be transformed into new play areas and restaurant items, including interactive trays.
Fernando Machado, global chief marketing officer at Burger King, said: "The UK market will be leading the way in making this first step towards change, which is part of our wider commitment on reducing plastics.
"Work is currently under way across all of our markets to look at how we can completely move away from non-biodegradable plastic toys by 2025."