A 10-month-old baby can safely drink about 4 to 8 ounces (approximately 120 to 237 milliliters) of water per day in addition to breast milk or formula. Water should be introduced after 6 months of age when solid foods are being introduced, but breast milk or formula remains the primary source of hydration and nutrition until 12 months

. Experts generally recommend offering small amounts of water, around 2 to 3 ounces at a time, not exceeding 4 ounces daily for babies between 6 and 9 months, and up to 8 ounces by 9 to 12 months

. Excessive water intake before 12 months can displace important nutrients from breast milk or formula and may lead to water intoxication, which is dangerous

. Signs of adequate hydration include 4-6 good wet diapers per day, while signs of dehydration or overhydration should prompt consultation with a pediatrician

. In summary:

• Water introduction starts after 6 months.
• Limit water to about 4-8 ounces per day at 10 months.
• Continue breast milk or formula as the main source of fluids and nutrition.
• Offer water in small amounts, preferably from a cup to encourage drinking skills.

This approach balances hydration needs without compromising nutrition or safety for a 10-month-old infant.