Is it ok to let a 2 month old baby to drink a sip of water? Maybe aboout 5 to 10ml?

It's not recommended. Giving water to a newborn can disrupt their feeding. It may even cause health consequences if given too much water - since the kidneys are not yet mature and too much water will release sodium along with excess water, and loss of sodium can affect brain activity. Your breastmilk or formula milk (given at the right ratio of powdered milk to water) will be enough to keep your baby hydrated.