RESTRUCTURING - Schedule of Restructuring Reserves Rollforward Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 28, 2024	Dec. 30, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	$ 143
Cash payments	(22)
Restructuring Reserve, Accrual Adjustment	(84)
Project reserves	37	$ 0
European Cereal Supply Chain Network Reconfiguration
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	78
North America
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	65
Europe
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	78
Employee related cost
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	45
Cash payments	(7)
Restructuring Reserve, Accrual Adjustment	(1)
Project reserves	37	0
Employee related cost | Europe | European Cereal Supply Chain Network Reconfiguration
Restructuring Cost and Reserve [Line Items]
Project reserves	37
Asset related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	23
Restructuring Reserve, Accrual Adjustment	(23)
Project reserves	0	0
Asset impairment
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	60
Restructuring Reserve, Accrual Adjustment	(60)
Project reserves	0	0
Other Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	15
Other cost
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	15
Cash payments	(15)
Restructuring Reserve, Accrual Adjustment	0
Project reserves	$ 0	$ 0