Unseasonal rain in Sri Lanka the past few days means Sunday's crucial match in Kandy could be reduced to as few as five overs per side.
"I think you just have to prepare as if it is a T20," Brook told reporters.
"I think you can sometimes go down a bit of a rabbit hole thinking that you're going to play a five-over game and then it ends up being a T20 and you kind of play it slightly differently.
"So I think we've just got to prepare as if it is a T20 game and hope that the rain stays away.
"And then if it doesn't, then we've got to adapt."
Brook indicated that a five-over sprint could mean a change in the batting order as they go "hell for leather" in search of fast runs.
"There's going to be some changes so we're not too predictable," Brook said.
"I want us to go hell for leather in 20 overs anyway, go out there and really take it to the opposition with the bat."
The inclement weather and a pitch that has been sweating under covers mean England will delay naming their side until Sunday's toss, breaking with their tradition of announcing their eleven 24 hours in advance.
Despite a stuttering group campaign, Brook's side are returning to the venue where they swept a T20 series against Sri Lanka 3-0 this month on the eve of the T20 World Cup.
"We can take a lot of confidence having played here and experienced this surface and this ground," said Brook.
But he cautioned that some of the Sri Lankans were in better form now, especially opening batsman Pathum Nissanka, who scored a century against Australia on Monday.
"Some of their batters are batting really well. So hopefully we can get a few wickets in the power play," he said.
"And Nissanka is on a bit of a heat at the minute. So it would be ideal if we can get him out early."
"We just want to go out there and play our best cricket and put them under pressure as much as possible all the way."
