Coffee is one of the best products from Uganda, but the British hooked the locals on tea, so finding a decent cup of native joe is nearly impossible, especially outside of Kampala. In Kampala, try the coffee house 1000 Cups on Buganda Road. The Source Cafe in Jinja sells Ugandan coffee at the airport, Banana Boat stores, and many hotels. The coffee is marketed under the name Kiira Kawa River Coffee. Good African Coffee and Cafe Pap are good restuarants for food or coffee in the Kampala area. In Jinja, stop by the Source Cafe for an incredible cappuccino--they had the sweetest espresso machine! or when you are in the west at Hotel Mountains of the Moon in Fort Portal
Chai tea is available widely, and is best in the rural areas near the tea plantations. You will see signs posted on shops and kiosks where it can be purchased.
Lower-end South African wine can be had in some restaurants, but stick with the beer. Any of the four major brands are acceptable, though the Pilsner brand is the only one made without added corn sugar for those who care about such things.
Be advised to drink Bottled water, usually called mineral water in local restaurants. Water flowing from taps is not treated.