Severn Trent Water has restored water supplies to Jaguar Land Rover and Cadbury plants in the Midlands.
The plants had to close on Monday due to water shortages caused by burst pipes in the region.
Severn Trent said it had worked "round the clock" to fix water supply problems caused by the big thaw.
"We'd like to thank the few businesses we've been working with over the past couple of days for all of their help," it said.
"It is our normal procedure to work proactively with a handful of large businesses who use a lot of water to manage their usage when we need to prioritise customer supplies.
"It enables us to make sure we have enough water for households and vulnerable customers including hospitals and care homes."
The water supplier said it had ramped up production at its treatment works and used tankers to support local hospitals.
On Monday evening, Jaguar Land Rover said workers at its Solihull plant had been sent home.
The company employs 11,000 people at the Solihull site in the West Midlands, which operates a pattern of three shifts a day from Monday morning through to Saturday morning. The plant produces 300,000 vehicles a year.
Cadbury owner Mondelez had said on Monday that it had limited water supply to its site in Bournville and some manufacturing was running, but maintained that it had enough stock.
It had earlier told workers to leave and work from home where possible.
Severn Trent covers a large region from mid-Wales to Rutland, and from the Humber down to the Bristol Channel.
The water supplier said it had seen nearly a 4,000% increase in reports of burst pipes due to the big thaw.