Only three kinds of crates in Command & Conquer: Red Alert 3 and Command & Conquer: Red Alert 3: Uprising: Credits, health and veterancy. And these cube-shaped items clearly label their contents by different symbols on their sides. Commander can consider to pick up or not by his own needs. Like Command & Conquer: Red Alert 2, health and veterancy crates have field effects, so better send units in tight formation to pick them up.