Pep up
Definition 1 of 2
Pro Tip 1/3Emotional Boost
Use 'pep up' when encouraging someone to be happier or more lively. 
I brought in cupcakes to pep up my team during finals week.
Pro Tip 2/3Casual Tone
'Pep up' is friendly and casual, not for formal documents or serious meetings. 
Let's play some dance music to pep up the atmosphere!
Pro Tip 3/3Energizing Events
Commonly used for livening up events like parties or gatherings. 
We need to pep up this party, it's a bit too quiet.