Botswana has excellent supermarkets and stores and you can buy everything you need for your safari when you arrive. Kasane and, especially, Maun are regional hubs supplying hundreds of hotels, lodges and self-drive visitors. Speciality liquor may be tricky to find, but all the basics are readily available.
Transporting fresh meat and fruit around Botswana can, however, be tricky, as veterinary fences have been established across large areas in an effort to contain foot-and-mouth disease. If you’re entering from South Africa, you’ll cross at least one checkpoint as you drive north and there’s another important control gate to the east of Maun. You can take meat from the south to the north and east to west, but the movement of fresh meat is strictly prohibited in the opposite directions.
The transport of fresh fruit and vegetables also goes through periodic restrictions, in this case to combat the spread of fruit flies. The rules around fruit and veg change regularly and are harder to pin down, but it’s generally not a good idea to bring any fresh fruit into Botswana, especially lemons, oranges and tomatoes. Botswana has excellent fruit, vegetables and meat so the best advice is to buy all your fresh produce in Botswana, avoid carrying fresh meat from Maun towards Nxai Pan, and otherwise just resupply as you go.
Most 4x4 campers come with extra jerry cans or built-in tanks for carrying water. Water management is important if you’re spending long periods in the bush, and drinking water is not available everywhere so top up with clean water where possible. You can fill up in the cities and larger towns, but many small villages have only a limited supply of borehole water. Park campsites usually have non-potable water or none at all. It’s a good idea to carry a few extra 5-litre bottles of shop-bought water as backup, and you may want to use these exclusively for drinking if you have a sensitive stomach.