Dogs should not drink caffeinated tea as it is dangerous and can cause fatality. Noncaffeinated tea is safe for a dog to drink, depending on the ingredients used.
Small amounts of caffeine overstimulate dogs and cause agitation. Large amounts of tea cause caffeine poisoning. While it takes more than a few cups of caffeinated tea to harm a dog, it is best to avoid.
In addition, any other products containing caffeine should not be fed to dogs. Coffee is just as dangerous to dogs as tea. Certain herbal teas may be given to dogs, but safety depends on the ingredients.