The regulators charged in June that the iPhone maker had breached the bloc's tech rules. The charge against Apple was the first by the Commission under its Digital Markets Act (DMA).
The fine is likely to come this month although the timing could still change, the sources said.
The fine would add to Apple's mounting antitrust troubles, as EU regulators attempt to level the playing field for smaller firms.
This comes just months after Brussels fined Apple 1.84 billion euros ($2.01 billion) in March for thwarting competition from music streaming rivals via restrictions on its App Store - Apple's first ever penalty for breaching EU rules.
Apple also faces an investigation into new fees imposed on app developers. DMA violations could result in a fine of as much as 10% of a company's global annual turnover.
The Digital Markets Act (DMA), which came into force earlier this year, requires Apple to allow users to set the default web browser of their choice on iPads, permit alternative app stores on its operating system and allow headphones and smart pens to access iPad OS features.
Apple declined to comment. The European Commission did not immediately respond to a Reuters request for comment.
Apple also lost a long-running court battle with the EU in September, resulting in the company being forced to pay 13 billion euros in back taxes to Ireland.
Bloomberg first reported on Apple's imminent EU fine earlier on Tuesday.
Watchdogs are readying the penalty after Apple failed to allow app developers to steer users to cheaper deals and offers outside of the App Store, Bloomberg reported, citing people familiar with the case.
($1 = 0.9153 euros)
