What do wizards do with their bonus action?

My current wizard build is twiddling his thumbs

If the wizard has a familiar, look and listen using its senses.

If an Illusionist, cast Minor Illusion.

Cast a spell such as Expeditious Retreat, Jump, Dragon's Breath, etc.

While this ship may have sailed if you're talking about a character you're already playing, it's worth pointing out there are several species options that offer bonus action abilities, including Aasimar, Dragonborn, Dwarf, Orc, etc. A lot of these are limited resources and/or very situational, but they're good to keep in mind.

I got a lot of use from Bigby’s hand. It’s a fifth level spell, so kind of a long wait until you get it, but it’s a great all-purpose control/damage spell. 
And the telekinetic feat can also be useful to help with positioning. Push or pull an ally out of danger, or an enemy into it, so you can lay down AoE spells to greater effect.

Im looking for zero resource options.  Cause sometimes combat gets pretty gnarly.

I didnt go with owl familiar, cause i didnt wanna do the help-flyby thing. But that seems to be what wizards are designed for.

I was thinking telekentic, but one issue is the dm usually doesnt use maps so a lot of theater of the mind make it hard to to detailed strategies like drop an aoe here, and telekentic push back in the guy who just ran out. The other issue is it doesnt do much without a concentration spell to push into in the first place.

Bonus action helping an ally out of a grapple could be a good use so the melee player can use their full action next turn to attack instead of wasting it trying to break the grapple.