Supplying is a mechanic where a unit restores all its fuel and ammunition. Supplying is completely free to perform. Supplying is usually done at the start of a turn, before combat.
The following methods are available to resupply a unit, for buildings the unit must start a turn on the building's tile. Rigs are able to supply all adjacent units when starting a turn, and then additionally move to supply additional adjacent units, allowing them to supply up to 8 units per turn. Supplying may be done at allied buildings.