If the answer above is None it means there is no specific mention in the legislation, but you still need to ask local law enforcement before drinking in Uganda.
It is prohibited for any licensee to sell, serve or supply alcohol beverages to anyone under the age of 18 years. The law provides an exception for anyone who is 16 or 17 years of age, and consumes a fermented alcohol drink with a meal, in a part of a licensed premises that serves meals and is not a bar.
You can find more legal details and links here:
Wikipedia Legal Drinking Page