Enchant a pickaxe with Efficiency V using an enchanting table at high enchantment levels
Combine two Efficiency IV books or tools on an anvil to make Efficiency V
Trade with librarian villagers for an Efficiency V enchanted book
Find Efficiency V enchanted books in loot chests
Use an enchanted book with an anvil to apply Efficiency V to a tool
Use commands in creative mode or with cheats enabled to give Efficiency V directly