Military equipment has long had some sort of process for self-destruction in order to prevent capture by the enemy. If they obtain functioning examples, not only might they press it into service with their own military, but more importantly, they can conduct exploitation. Thus, you'll find a "Zero" button on any modern radio system. Press it correctly, and the system goes blank. Do this just before capture (or if you have time in an aircraft, before ejecting) It's the modern equivalent of burning the codebook. Before electronic programming, the similar solution was an explosive charge on the radios, which goes back at least as far as WWII. Case in point, this is the self-destruct off a US Navy A-4 Skyhawk. https://cdn.shopify.com/s/files/1/1343/9895/products/DSCN6870_1024x1024.JPG?v=1474667377 Push both buttons at the same time, the explosive is detonated, and the radio (and IFF) blow.

In the event of something bigger having to be destroyed, oftentimes it's not a button but a process. For a tank, you'd use thermite grenades. Example, one on the breech block, one on the engine block. The thermite basically melts through the metal of the object, rendering it useless. It is important, when sabotaging equipment, that the same pieces be destroyed on all vehicles being destroyed, in order to prevent the opposition from being able to create a functioning vehicle by cobbling undestroyed components from multiple vehicles.

Fitting a vehicle with enough explosives or thermite to destroy itself at the push of a button is impractical for two reasons. One is that you would need a lot of it. The other is that battlefields are violent places, and you don't want a hard knock or some such to accidentally trigger the self-destruct feature of an otherwise operable vehicle. Hence the use of self-destruct only on specific components as the above-mentioned radio, and by use of manual charges. For the same reason, fitting equipment with an anti-tamper device such as a vial of acid which melts the electronics of a radio if poorly opened is not really practicable in combat systems, but could be used in less extreme situations like an office.

The one exception is a ship which comes with in-built destruction options. Scuttling the ship is a long-standing tradition, and could be done by fire or making holes. You can open sea-cocks to let water in, or just put a big explosive somewhere. When the armored ship Graf Spee was scuttled in WW2, they hung armed 11" shells above the main magazines by rope, poured fuel over the whole shebang, just to make sure that after she flooded, she wouldn't be raised. Open the seacocks, light the fire, and then get the hell away from the ship before the rope burned and the shell dropped into the magazine.

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