Semi-occluded vocal tract exercises are a great way to start your singing for the day (See article: Reset Your Tired, Tense Voice). Do some lip trills, fricatives (sounds like ff, sh, ss, th), or sing through straws.
Check out this video on how to use a straw to improve your voice:
Always begin with light glides, in other words sliding up and down in pitch but not too loud.
You vocal warm up shouldn’t take more than 15 -20 minutes. You can do this vocal prep at the same time you take your shower and have your breakfast.
Make noise all morning long. Consider this warm-up your routine of weird and annoying things in the morning.