Combat: Other Activity

Your turn can include a variety of flourishes that require neither your action nor your move.
You can communicate however you are able, through brief utterances and gestures, as you take your turn.
You can also interact with one object or feature of the environment for free, during either your move or your action. For example, you could open a door during your move as you stride toward a foe, or you could draw your weapon as part of the same action you use to attack.
If you want to interact with a second object, you need to use your action. Some magic items and other special objects always require an action to use, as stated in their descriptions.
The DM might require you to use an action for any of these activities when it needs special care or when it presents an unusual obstacle. For instance, the DM could reasonably expect you to use an action to open a stuck door or turn a crank to lower a drawbridge.
Interacting with Objects Around You
Here are a few examples of the sorts of thing you can do in tandem with your movement and action:
draw or sheathe a sword
open or close a door
withdraw a potion from your backpack
pick up a dropped axe
take a bauble from a table
remove a ring from your finger
stuff some food into your mouth
plant a banner in the ground
fish a few coins from your belt pouch
drink all the ale in a flagon
throw a lever or a switch
pull a torch from a sconce
take a book from a shelf you can reach
extinguish a small flame
don a mask
pull the hood of your cloak up and over your head
put your ear to a door
kick a small stone
turn a key in a lock
tap the floor with a 10-foot pole
hand an item to another character
Source: PHB, page 190. Available in the SRD and the Basic Rules.