Many employees were taken to hospital with stomach cramps, a spokesman for the Starlight Sweaters factory said.
Police said someone may have poisoned the water supply.
In April, more than 1,100 people were killed and about 2,500 wounded when a factory building collapsed near Dhaka.
The Rana Plaza collapse was one of the world's worst industrial disasters and sparked global outrage.
It has also led to violent protests as workers demand better pay and working conditions.
Up to 600 Starlight Sweaters workers are estimated to have fallen ill after drinking the contaminated water on Wednesday, factory spokesman Based Ali said.
"The workers have been sent to different hospitals after they reported  stomach pain and started vomiting," he said.
A local police officer told the AFP news agency the water supply was possibly "poisoned" with pesticides.
The factory is based in the industrial complex of Gazipur on the outskirts of Dhaka.
Clashes erupted earlier between police and garment factory workers as thousands of protesters took to the streets of Dhaka demanding better pay and conditions.
And in another demonstration, security forces fired rubber bullets and tear gas to disperse large crowds gathered at the site of the collapsed Rana Plaza buildings.
Many of the protesters were relatives of Rana Plaza victims asking for compensation.
Meanwhile, the UK has announced it will donate Â£18m for safety and skills training for thousands of low-skilled Bangladeshi garment workers.
Britain will also provide a team of experts to review the country's building inspection system.
Hundreds of Bangladeshi garment factory workers have fallen ill after drinking suspected contaminated water in their workplace near the capital Dhaka, officials say.